The latest version of WebSphere Application Server, v6.1, is now available.
Check out the press release from the announcement back in April, "IBM WebSphere Application Server V6.1 delivers flexible, secure infrastructure to provide a reliable foundation for your Service Oriented Architecture." For details of the announcement, see WebSphere Application Server V6.1 Announced. One of the main differences is that WAS v6.1 runs in Java SE 5 (see IBM Java Developer Kits: Java 5 SE) whereas WAS v6.0 runs on J2SE 1.4; both WAS v6.0 and v6.1 implement J2EE 1.4.
There are the usual Base, ND, and z/OS editions. (How many J2EE app servers run on mainframes?!) There's now v6.1 documentation, including the v6.1 InfoCenter.
If you're a Passport Advantage member and licensed for the latest releases, you should be able to download WAS 6.1 now. (If you're a WAS customer/client, can you confirm that WAS 6.1 is now available for download? Please add a comment.)