This is a list of all the legal sets that are allowed to be used in extended as of right now and a specific list of cards that are BAN in extended play.
Ban Cards
* Aether Vial - http://gatherer.wizards.com/Pages/Card/Details.aspx?name=Aether%20Vial
* Disciple of the Vault - http://gatherer.wizards.com/Pages/Card/Details.aspx?name=Disciple%20of%20the%20Vault
* Sensei's Divining Top - http://gatherer.wizards.com/Pages/Card/Details.aspx?name=Sensei%27s%20Divining%20Top
* Skullclamp - http://gatherer.wizards.com/Pages/Card/Details.aspx?name=Skullclamp
Legal Sets
* Ninth Edition
* Tenth Edition
* Magic 2010
* Mirrodin
* Darksteel
* Fifth Dawn
* Champions of Kamigawa
* Betrayers of Kamigawa
* Saviors of Kamigawa
* Ravnica: City of Guilds
* Guildpact
* Dissension
* Coldsnap
* Time Spiral
* Planar Chaos
* Future Sight
* Lorwyn
* Morningtide
* Shadowmoor
* Eventide
* Shards of Alara
* Conflux
* Alara Reborn
* Zendikar
* Worldwake (effective February 5, 2010)
* Rise of the Eldrazi (effective April 23, 2010)
If you have any questions feel free to ask, keep an eye on this incase more ban cards come up or if you have questions pertaining to why cards are ban.