FreeBSDCon is a brand new thing, and it would seem to be the only "BSD-specific" national convention. However, OpenBSDers, NetBSDer, Linuxers, or what have you are all welcome. If you look at the speakers, you'll note that while there are FreeBSD-specific topics, most of them are pretty agnostic across the BSDs. Even if you don't run FreeBSD in particular, you'll find a lot to be interested in. Hey, the FreeBSD-specific ones should be especially interesting then, eh? :)

I really wish I could go this year, but I didn't plan for it, so it's a near impossibility. FreeBSDCon promises to be a lot like USENIX, and I would expect a diverse turnout. I'd love to have the opportunity to actually meet the people I work with all the time.