Adobe Apollo public alpha release is now at Adobe Labs (http://labs.adobe.com/wiki/index.php/Apollo).
You can reach release notes to get more information about the current release.
You can download and install on your Windows or MacOSX platform.
Here are some other useful Apollo links:
Free Apollo Training From Lynda.com
http://movielibrary.lynda.com/html/modPage.asp?ID=378
Sample Applications
http://labs.adobe.com/wiki/index.php/Apollo:Applications:Samples
Apollo Camp San Francisco
http://labs.adobe.com/wiki/index.php/Apollo:Camp:03162007
Apollo for Adobe Flex Developers Pocket Guide
http://labs.adobe.com/wiki/index.php/Apollo:Books:Apollo_for_Adobe_Flex_Developers_Pocket_Guide
Apollo Forums
http://www.adobe.com/cfusion/webforums/forum/categories.cfm?forumid=72&catid=641
