I know Jackson says 6/6, as does the new girl bringing news today, and SelfPraise said he hadn't heard anything but 6/6 or 6/13, but I think May 28th or 29/30 (weekend) makes perfect sense and will end up being the correct date. The main argument against it is that it's memorial day weekend and many people will be traveling and not focused on buying a phone, but personally I would definitely not hesitate to cancel or postpone my vacation if it competed with getting the EVO on day one.
If they announce the price/date on the 12th, it would be just over two weeks till the 28th, but 3 and a half weeks until June 6th. Most new phones are available for sale 2 weeks after the release date being announced. Official Droid release info was given on 10/22/2009 and was available on 11/6/2009, Palm Pre was announced 5/19/2009, available 6/6/2009, htc Incredible was announced on 4/14/2010 and was available on 4/29/2010.
All those were right around two weeks. So I'm going with a May 12th announcement, and memorial day weekend availability. It stays ahead of the iphone frenzy, and matches up with the Prince of Persia opening. If the date is officially on saturday, the 29th, it would be cool if bestbuy or sprint stores had a special midnight release party the night before. It's a pretty nerdy thing, and I'm not a COMPLETE geek, but I would SO be there!