Currently all releases are made through SourceForge and can be found here. For each version there is a source release and binary releases for Linux, Windows, Solaris, and Darwin (includes OS X).
Debian packages can be found here.
Mac OS X users, be sure to check out MacFLAC, a FLAC distribution specifically for OS X, including a .pkg installer and applescript droplets.
You can also get the nightly CVS tarball here.