ADV, or A.D. Visions, Inc, is based in Houston, Texas, and is one of the premiere anime licencing companies in North America. Though they also hold licences to titles such as Farscape and Andromeda, ADV is most known for their anime releases, with 10 16 (I believe this was the number I heard at Otakon) different production teams handling a variety of projects.

As far as which titles they have, it is suffice to say that there are a lot of them. So many, in fact, that it would be futile to list them all. Instead, here's some of their more well-known, older licences.
And here's some new stuff: In all seriousness, ADV is an industry powerhouse, and their industry panels at anime conventions across the world are always packed, not only because of the number of press that cover the panels, but in part due to the number of otaku who want to be among the first to hear what's next. They give out some pretty cool stuff (the latest DVDs, for example), and voice actors like Tiffany Grant make appearances (I got her to do my voicemail message as Asuka Langley Sohryu. No kidding.) Recent announcements (at Anime Boston 2003) included the licencing of Final Fantasy: Unlimited, the licencing of Azumanga Daioh, the licencing of Evangelion: the Director's Cut Episodes (eps 21 through 26) and something called Magical Shopping Street Abenobashi (known in Japan as Abenobashi Mahou Shoutengai).
Update: Since this (now somewhat outdated) writeup, ADV has begun many new ventures, including contributing to the up-coming live action Evangelion film, which is also being spearheaded by Weta Workshop and Gainax. Abenobashi is being released as Magical Shopping Arcade Abenobashi, the Eva Director's Cut episodes have been re-released in two volumes (Ressurection and Genesis Reborn), and AzuDaioh's first volume is set to hit shelves in April of this year. Notable licence aquisitions in 2004 include GetBackers, a title which will surely be looked forward to by many.