What's the best site to look for open source projects to work on for someone who's a newbie to FOSS, but with some development experience (Java and C++)?
Sourceforge, ohloh, and freshmeat are the ones I know of.. Sourceforge is a major pain to use though since like their 6th time to redo their entire site and introduce new flaws and bugs into their interface though
As a java developer you might also consider Apache- not just the httpd server. There are also a lot of projects located on Google Code and if you are happy with git and like the idea of software dev meets facebook, you might also try GitHub
If there's a specific project you're interested in many projects maintain their own websites too.
Linux or Open BSD DVD. I am not joking, first learn things and then go for FOSS or No Foss.
It is not a site but a lot of FOSS people hang out and chat on #freenode. I know it is the age of twitter and so on but IRC plays a crucial role in FOSS that twitter can't approach.