You see right under the Dual-boxing.com banner theres a bunch of tabs like Portal, Forums, Rules, etc. click the one that says keyclone.
I don't have Bartender so i can't tell you anything about it. I do recommend Jamba...even though i don't use it, but it seems other boxers enjoy it quite a bit.
Addons i use:
X-perl -> UnitFrames
TitanPanel -> coords, bag space, durability, other stuff
Atlas and AtlasLoot Enchanced -> instance maps and what drop from bosses along with a boat load of other goodies
Deadly Boss Mods -> Mostly just for AV timers on towers but also gives warning for special boss attacks
Auctioneer -> selling stuff easier in the AH
Proximo -> Helps with targetting in arena