I've been playing off and on with open solaris. For those of you who fancy a dabble but don't find spending an hour or so building vm's a useful and enjoyable way of spending your time sun have launched a we browser based sandbox service enabling you to access an open solaris session through a browser.
Your mileage may vary on this - I found it so slow and had so much network latency as to be almost unusable, but then I'm a long way away topologically from the learning centre.
That said it's worth a go if you're at all curious to see what it looks like. And providing a demo service does make access to seeing what it looks like (and convincing people it's not a finger in the ear exercise in complexity) that little bit easier.