My HTC legend give me the ability to associate my contacts' various accounts in the People application (ie. email, Facebook, Twitter...). Is this a HTC only feature? If it is, is there an alternative for non-HTC phones?
The people application itself is an HTC exclusive, but merged contacts from multiple sources (GMail, Exchange, Twitter, Facebook, SIM, carrier phonebook, etc) is a standard Android feature for 2.x (maybe earlier). By default the system tries to intelligently merge identically named contacts, but you can manually add/remove contacts from the merged identities.