If you want to talk about some project you are doing (using Crystal Space) or you have a question about Crystal Space or CEL then you can visit the forums. Registration is required (due to spam problems).
If you prefer mailing lists then you can also subscribe to a number of our mailing lists that you can find at the Crystal Space SourceForge page. There are a number of mailing lists there including one where you can keep track of all developments that we are doing in Crystal Space (crystal-cvs mailing list).
If you have a quick question or just want to chat about your project then you can visit the #CrystalSpace IRC channel at FreeNode.net. If you have a more art related question then you can visit #CrystalSpace-arts on the same IRC network.
We have a number of blogs that you can read as well.
Projects using CS
Ohloh.net has a page with statistics for Crystal Space. What you can look at are lines of code, programming language distribution, author commit stats, and some more. Perhaps most interesting is to compare with other projects. Crystal Entity Layer also has a page there.
On this page you can also find various statistics on Crystal Space. These statistics are gathered directly from our SVN repository.
DevMaster.net has a collection of graphics engines. Of course, Crystal Space is present there as well (in the category Open Source engines). You can also write reviews for engines and vote for your favorite one (i.e. Crystal Space).
There is a FreshMeat page for Crystal Space.