Karen Klein, who lives in the Rochester, N.Y., suburb of Greece, was tormented by four 13-year-old boys who hurled profanity-laced insults at the grandmother.
Video of the incident posted to YouTube went viral.
After seeing the video, Toronto resident Max Sidorov set up a web page on the fundraising service Indiegogo.
Sidorov, who said he was a victim of bullying himself as a young immigrant from Ukraine, originally set the fundraising goal at $5,000 so Klein — who lives on a salary of $15,000 a year — could be treated to a vacation.
As of 10 p.m. ET Friday, the fund had amassed more than $593,000, with 29 days remaining on the page's countdown.
"I felt deeply sad for Karen," said Sidorov, a 25-year-old nutritionist and graduate of York University. "I had some issues with bullying myself when I was a young kid and had just come to Canada, so I know where she's coming from."
Bus monitor overwhelmed by support
Klein said on CBC-TV's Connect with Mark Kelley on Thursday that she was overwhelmed by supportive emails, Facebook messages and flowers.
"It certainly has been an experience — one I'll never forget," she said.
Klein said she hasn't yet decided where she might go on vacation.
On Thursday, Sidorov said he also hoped the money could allow Klein to stop working.
The incident has led to calls for harsh punishment for the boys behind the bullying, who are reportedly under police protection.
"They've received death threats," Greece police Capt. Steve Chatterton said Thursday. "Their families have been threatened.
"We have custody of one of their cellphones, and he had over 1,000 missed calls and 1,000 text messages threatening him. And he's 13 years old. That must stop."
Despite Sidorov's efforts to help Klein, he has been accused of using the campaign to promote his own nutrition book.
Sidorov said he provided a link to the book on the fundraising campaign page because people kept asking how they could help him in return.