Nadene Lomu posted a link to the page on Facebook this morning, asking supporters to "please help me and our sons bring Daddy Jonah Lomu's dreams and visions to life".
Givealittle said the reason their website had crashed was linked to the fundraising page for Lomu.
Lomu (40) suffered a cardiac arrest shortly after returning from a post-World Cup break with his family in Dubai and died at his Epsom home early yesterday.
"It is with the saddest times, while my heart aches I share with you all a vision which Jonah and I had set out to do together," she wrote.
"I promise my dear husband, all that we said we were going to do together, I will do everything and more...you blessed the world with your presence and now the world will celebrate the great man you were and will always be."
On the Givealittle page Mrs Lomu describes herself as Jonah's best friend. "Jonah and I had big plans to make a difference in the world with all that he learnt," she said.
She said he would always be a "great husband, father inspiration and icon to the world" and he and she wanted to build a lasting legacy with the support of his fans.
"Jonah has left this Earth too soon leaving us all empty-hearted. Through Jonah's strength which remains in our two sons and myself, with his spirit that will forever be by my side, my promise is to bring the visions we both had planned to do together."
Mrs Lomu did not give any specifics on how she would fulfil her late husband's dream but vowed to make a difference.
"I will now do this alone and we will make a real difference. With the support of his great global family and all his boys, here I will finish building the legacy that my wonderful husband created when he burst onto the international stage leaving history and our hearts, changing the face of rugby."
Nonu, Hart pay their respects
Since Lomu's death a stream of visitors have come and gone from his house. Former All Blacks coach John Hart and All Black Ma'a Nonu visited Lomu's home this morning to pay their respects and lend support to the family.
All Black Ma'a Nonu entered the home - where well-wishers had left pink camellia blossoms outside - dressed in a hoodie and wearing sunglasses. Hart arrived at the house carrying a homemade chocolate cake.
Yesterday former All Blacks Michael Jones, Eroni Clarke and Ofisa Junior Tonu'u. Many brought flowers and wore dark clothing, and gathered to farewell a silver hearse as it left the property yesterday.
Funeral plans were still being determined, a spokesman for the Church of the Latter Day Saints, which Lomu and his wife are members of.
A church spokeswoman has confirmed that Mormon leaders are supporting Lomu's family and helping them with planning for the funeral.
No date has been set for the ceremony but it is likely to be held at an LDS Church in Auckland.
New Zealand Rugby spokesman Mike Jaspers said it was too early to say if the organisation would have any involvement in the funeral arrangements.
Brother's love
Lomu's younger brother John paid his own tribute, with a touching photo of the two as children.
Dozens of people, including former heavyweight boxer David Tua, commented on the photo, sending their love to the Lomu family.
Tua wrote: "Deepest 'ofa (Tongan for love) for you my uso (brother) at this time of sadness for the passing of your toko (brother). The legend Jonah Lomu #11 - our prayers and condolences to your whole family. Ofa lahi atu. (With much love, in Tongan).
Amid Lomu's much-publicised illness, The Hits presenter Grant Kereama donated a kidney to him in 2004.
This morning Kereama and fellow presenter Polly Gillespie aired an emotional message to listeners as they mourned the death of their close friend. In a recorded message, the pair explained why they were absent from their show.
Kereama said: "Hope you guys understand, eh? I really can't talk."
Gillespie said the pair weren't in a position to be on the radio this morning.
"I think you know that when something really affects you and there's something really important, there are no words and there's no way to go on and even speak to your very best friends without being really emotional," she said.
"We have lost one of our best friends. Today we will not be at work. I hope you understand."
International celebrities also shared their shock over the death of Lomu.
Actor Morgan Freeman wrote that he is "heartbroken" to hear of his passing. "His strength and passion were a source of inspiration to us all."
David Beckham also offered his condolences, saying how sad he was to hear of the passing of "this amazing giant of a man".
One of the men who helped make Lomu famous, former England fullback Mike Catt, remembered a "freak of nature" who set the rugby world on fire.
It was Catt who Lomu rumbled over as television commentator Keith Quinn memorably stumbled over his words: "Lomu ... oh ... oh ..."
"When Jonah came running at me I'm thinking, 'right, get your feet close, I want to drive through the player'. Unfortunately, all I remember is him scoring the try behind me," Catt recalled of the 1995 World Cup semifinal, where Lomu's four tries led the All Blacks to victory over England.
"For me to be making a tackle, he's obviously run through 14 blokes to get to me as the last man of defence."
Catt blamed English captain Will Carling for Lomu running over him. Lomu was off balance after Carling ankle-tapped him.
"That's probably the reason he's running straight over the top of me, because otherwise he would have just run around me like he did three times after that."
Fame never changed him
Lomu made his debut for the All Blacks against France in 1994. Both games were lost and Lomu was cast aside until a surprise callup for the World Cup the following year.
His first All Blacks captain Sean Fitzpatrick told Newstalk ZB this morning Lomu wasn't originally part of the team plan at the Cup, but an injury to Eric Rush gave him his chance.
"Little did we know we were going to have a 19.5 stone, 6.5ft winger. He was just a revelation. He broke the mould about what rugby players should do," Fitzpatrick said.
"The legacy he created was basically done in the space of about five or six games really."
But that never changed him.
"He was the most wonderful person, very gracious, very humble. He was almost embarrassed by the adulation he received after 1995.
"I can honestly say we never had any issues with him thinking he was bigger than the team. I think that says so much about the person. He was a good man."
Fitzpatrick fondly recalled Lomu leading non-playing members of the historic 1996 touring team to South Africa in a victory haka, as a weary All Blacks beat the Springboks in a series at home for the first time.
All Blacks skipper Richie McCaw paid his tribute last night on social media, saying he couldn't believe the sad news of Lomu's passing.
"Jonah was an incredible rugby player and a top bloke. My thoughts are with his family. Rest in peace mate," McCaw wrote on Facebook.
Lomu publicly revealed he was battling kidney disease in 1997.
His coach at the Auckland Blues at the time, Graham Henry, said today he had no idea the big man was struggling.
"We always questioned his fitness - when I was coaching him in '96, '97, we didn't know anything about the kidney problem. So we did a 3km run as part of the fitness test in those days and he was always last," Henry told TV3 this morning.
"We always had to try and get a mate to run beside him to push him along. And I didn't find this totally acceptable ... So I gave him a bit of a nudge. But we found out [about his disease] later."
'Traumatic time'
In a statement yesterday, Nadene said it was a "traumatic time" for her family, especially the couple's young sons, Brayley, 6, and Dhyreille, 5.
"It is with great sadness that I must announce my dear husband Jonah Lomu died last night.
"As you can imagine this is a devastating loss for our family."
Mrs Lomu requested privacy for herself and children, but other family members spoke about their loss.
Nehoa Lomu first heard about his younger brother's death on the radio, and said their mother, Hepi, was upset "like any mother would be".
"What happened, happened. But we are very proud of my brother and what he did for New Zealand and also Tonga."
This morning Lomu's cousin Mataiasi Lomu has posted a tribute, saying the name "Lomu" would give his family strength.
"As I keep on with my day knowing that I knew Jonah. Not as the rugby player, nor as the left winger, nor the one to wear #11. But as my cousin and brother to me, his siblings and the rest of my cousins who carry the name Lomu," he wrote on Facebook.
Lomu's first wife Tanya Michaels - formerly Tanya Rutter - said his death left her "lost for words".
"May his soul rest in peace. A bit lost for words at the moment but when I am ready and have gathered all my thoughts I will have pay a tribute to him and his family!!! Love Tanz," she said in a brief Facebook post.
New Zealand Rugby chief executive Steve Tew said it was an "incredibly sad day" and organisation was working to support Lomu's loved ones.
"There's a lot now to obviously work through but we should reflect on the amazing contribution Jonah made."
Former long-time All Blacks doctor John 'Doc' Mayhew told the Herald that Lomu's well-known kidney issues would inevitably have contributed to his heart stopping.
Dr Mayhew said people with chronic kidney disease had a higher chance of heart problems.
