A very neat, consise posting detailing some of the fancy features in OpenSolaris. News to those that know Linux well, but have been out of the Solaris loop for some time.
So you've been playing around with alternative OSes for a while and you reckon you've got this Linux thing mastered. Maybe you're tried Mac OS X and found it a bit too restrictive (or expensive); perhaps you've kicked the Hurd's tyres and thought you'll come back to it when it's something more than just a clever name.
If you're looking for something else to play with, we humbly suggest OpenSolaris. Like Mac OS X, which we looked at recently, OpenSolaris is based on Unix; also like OS X, it's best known for running on a specific processor (in this case Sun's SPARC architecture) but now works on a range of architectures including x86. Unlike OS X though, OpenSolaris is open source, so you can download it for free and start fiddling with it.