THIS POST IS NO LONGER UPDATED.
Thanks to the new community site, it's become far more practical to maintain this information in wiki format.
For the most recent version of the LFR Legality list, please click here: community.wizards.com/lfr/wiki/Legal_Opt...
(In fact, merely editing this post to put the above notice in place completly destroyed the formatting of the old list.)
See something missing/wrong with the new list? That's the beauty of a wiki - YOU can log in and make changes. We only request that you please remember to leave a note in the "summary" box about what you changed so that other wiki editors can review those changes later.