Great news! Sriram anncounced the availability of the upcoming Sun GlassFish Web Stack 1.6 as development and testing version for Solaris 10 U5+ and RHEL 5.2+.
The development version is currently only available as IPS (Image Packaging System) distribution which basically gives you a small installer like application allowing you to download and pick only those components you're really need. IPS also allows you to pick up updates easily and - for me - the most impressive feature is the non-root install and the ability to place your web stack anywhere you want in the directory tree of your system. So you don't need to have root access and you can install web stack as a regular user. That's quite an amazing feature. And as far as I know no other web stack software for Unix offers this kind of feature.
Find all the details at Siram's blog: Web Stack 1.6 development builds are available for testing.