GlassFish v2 just hit beta candidate (the beta release date is Feb 26th) and I'm taking the opportunity to describe a couple of new features we have added for that release:

• Grizzly now support Comet processing (here and here). Comet is a programming technique that enables web servers to send data to the client without the client needing to request it.
• Improved Virtual Server (Host) support (here and here)
• Greater flexibility in configuring your web application's class path (here)
• Supports for Eclipse's JDT Compiler (here)
• JSP compilation with JSR 199 (here)
• Apache AJP official support (here, here and here)
• Extending the Web Container (here)
• JRuby On Rail supports via Grizzly (here)
• WebDAV and CGI support (here and here)
• HTTP Compression support (here)
• SSL support now use NIO non blocking (here)
• Port Unification (here and here)
• New Support for Virtual Directory Mappings (here)
• (near) Zero (re-)Deployment Time for JSF (here)
• JSF RI Performance/Scalability (here)

I'm sure I probably forgot some, but that's a good start. If you have free time, just try the beta and file bugs!