Internet Explorer 8 Beta 2 will be aimed at the end-user (the first beta was aimed at the web developer) and, while all its features haven't been disclosed yet, we already know about some expected reliability and performance improvements. The next beta version is scheduled to arrive sometime next month and, while it will be a public beta release just like Beta 1 was in March, Microsoft is asking for more quality testers for its beta program.
Anyone can currently discuss the betas on the IE8 newsgroup (monitored by Microsoft MVPs and IE team members), and can vote on IE8 bugs reported by testers via Microsoft Connect. However, the company feels this isn't enough, since the only direct way to file a bug report is to be an official tester. So the IE development team is looking for more users willing and dedicated to improving the next version of the world's most popular browser. Microsoft is asking anyone interested in filing bug reports to e-mail the team "a little about yourself including why you'd be a great beta tester."
Usually the company relies on surveys or beta invites, but it appears that the software giant is only looking for truly dedicated testers in this beta program. Microsoft doesn't have much time (about four months) after the release of Beta 2 in August if the company wants to get the final version of IE8 out the door by the end of the year. There has not yet been a mention of a Beta 3 but, given the timeframe Microsoft has and the fact that RCs still need to be released, even assuming that there will be no delays, the release of yet another beta is unlikely.
Further reading:IEBlog: Wanted: IE8 Beta Testers