Currently the only supported formats are Standard, Extended, Vintage, Legacy and Modern. Personally, I think Extended ought to be removed, as that one has been retired, but Commander could still be added. There are other formats, too, that could be added:

https://en.wikipedia.org/wiki/Magic:_The_Gathering_formats

I could see this going either way. On the one hand, almost every card ever printed is legal in Vintage. The only ones that aren't are Ante cards, the Conspiracy cards, and a few others (Chaos Orb, Shahrazad and such). But on the other hand, Commander has it's own banned list.

Perhaps the best solution is to mark a card with ALL formats in which it is legal.

For Commander, is it multiplayer or one-on-one? There are two different ban lists for those formats, neither of which is official.

Multiplayer ban list:
http://mtgcommander.net/rules.php

Duel ban list:
http://duelcommander.com/banlist/

Commander has an official banned list:

http://archive.wizards.com/Magic/TCG/Resources.aspx?x=magic/rules/100cardsingleton-commander

terrafrost wrote:Commander has an official banned list:

http://archive.wizards.com/Magic/TCG/Resources.aspx?x=magic/rules/100cardsingleton-commander

That banned list applies only to MTG Online. On the page you reference, there is a link to the official banned list for the format, and it is the one at MTGCommander.net. Commander is a fan-developed format, so WotC does not maintain the official rules or banned list (except for that format in MTGO), though it does have legal ownership (copyright) of the term, "Magic: The Gathering - Commander".