TeX Live 2007 is available online now, and was available on DVD and CD as of May 2007 (depending on mailing vagaries) to members of most TeX user groups.
TeX Live 2008 is in preparation: we are aiming for a summer release. This year, we do not expect to make physical CDs for user groups, but only the DVD, for the simple reason that even with the best compression we know of (lzma), it no longer fits on a 700mb CD, and the programming time involved in supporting other alternatives is better spent elsewhere.
Please try the 2008 test releases if you can: either (recommended) the small bootstrap installer available on CTAN (master on tug.org). or (not recommended) giant ISO or tarball images.
If you have problems running TeX after installation, the first thing to check is your environment variables: settings that end up referencing other TeX installations (TeX Live or otherwise), can clearly cause trouble.
Bug reports are especially welcome, since these are test images. Any problems not found in testing will be present in the real release, so please do test anything you can. In general, please email tex-live@tug.org with any problems, questions, suggestions. The tex-live list archives may be of some use.
If you wish to obtain TeX Live through TUG, please become a member of TUG. The TeX Collection, including TeX Live, is distributed as a benefit of membership to TUG members each year. (Since there was no TeX Collection in 2006, the 2007 release will be sent to both 2006 and 2007 members.) You'll also receive a year of TUGboat, among other things. (Alternatively, you can purchase any of these items from the TUG store, without becoming a member.)
Most other TeX user groups also make TeX Live available to their members; please contact whichever you are interested in for details. TUG encourages you to join whichever user group is best for you.
You can download the zipped TeX Live ISO image from CTAN. It is almost 1GB. If such a large download is problematic for you, please see above for obtaining it on DVD or CD.
For the 2007 release, there are two images:
tug.org's bandwidth is provided by the University of Aarhus in Denmark. In order not to abuse their hospitality, we ask you to use CTAN or BitTorrent rather than tug.org to download the TeX Live release.
The last general update of packages and programs for the 2007 release was made on 1 February 2007. For more recent versions, please consult CTAN.
At present, the original TeX Live regrettably does not support incremental updates. (This is an area of ongoing development.) However, TeX Live has also been repackaged for many GNU/Linux distributions; see the TeX Live and Debian web pages, for one. The MacTeX distribution, which we recommend for MacOSX users, is also based on TeX Live. All of these methods support ongoing updates.
Older releases of TeX Live are available for historical purposes.