Some 85,000 passes for the Sept. 26 event in the Austrian capital are up for grabs on http://www.tribute2009.com. Prices range from about euro60 ($85) to more than euro500 ($712).
Event promoters say the Web site crashed more than half an hour before the sale was due to start at 11 a.m. EDT after a million people had accessed it.
Jackson's brother Jermaine is expected to name the performers in the next two weeks.
The tribute will take place at a 17th century palace. Jermaine Jackson has said Vienna was chosen as the venue because his brother "loved castles."
Michael Jackson died June 25 at age 50.