- Long-Term-Support (Dapper, 6.06, as of this writing)
- Current (Gutsy as of this writing)
- New alpha/prerelease (Hardy Heron 8.04 Alpha 4 as of this writing)
Once Hardy is released, these will shift one-to-the-right, along with the next pre-release (Intrepid Ibex).
Please also note that you can always get a the 64-bit amd64 version on request, although the 32-bit i386 version is the default.