Louis asks "which BSD"? In my opinion, if you have x86-based servers, go with OpenBSD 3.0 for its emphasis on security; although between NetBSD, FreeBSD and OpenBSD I would say that there are no bad choices. The recent changes to their filesystem code greatly increase performance while maintaining filesystem integrity. Note that you need to apply the one-line fix that Connie Hentosh posted on this bboard to have the best reliability, and should probably add the tcl exec fix if you are using exec a lot, or running OpenACS4.
For Linux, Debian is your best bet. Their package management is just the way to go, period.
