Do you want a 'use my system/distro war' on this forum?
fpc is available out-of-the-box for FreeBSD, Linux and OS/X. So I choose one of those.
And if you're using Linux, a lot of distributions have fpc included. And my guess is that Fedora is the most up-to-date (as far as fpc/lazarus is concerned) and with the new Fedora-11 with the new GDB debugging can become awesome...
But, hey, that's just my choice.