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, and Darwin (includes OS X).

Debian packages can be found here.

You can also get the nightly CVS tarball here.

GUI front-ends:

• Windows
  • There is a Windows GUI appropriately called FLAC frontend.
  • Monkey's Audio can be fooled into supporting FLAC as an external encoder; here's how. If you like it, be sure to ask Matt to add support for FLAC officially!
• Unix
  • Grip is a great ripping and encoding front end and can be easily configured to use flac.