There's an article on wow.com and the comments indicate a lot of interesting Vent alternatives.
http://www.wow.com/2010/05/23/breakfast ... h-to-talk/
I'm thinking of installing Mumble (http://mumble.sourceforge.net/) on evilkitten.
Vent alternatives
Moderator:Lamas
TEAM CLERIC: Allern, Dranei Paladin; Lothlondor, Night Elf Druid; Lelian, Human Mage; Lesasia, Human Death Knight; Lagervolk, Dwarf Hunter; Sylerissar, Night Elf Rogue; Langston, Worgen Warrior; Leanora, Gnome Priest
WE SPLIT THE PARTY: Renethal, Blood Elf Paladin
WE SPLIT THE PARTY: Renethal, Blood Elf Paladin