Just came across an apparently free online service called EQO. Like iSkoot, the service's client will allow you to Skype your friends. But unlike iSkoot, EQO also allows you to IM your contacts in popular programs like GoogleTalk, Yahoo Messenger, and AIM. And EQO supports a lot of phones (supported manufacturers begin with "Alcatel" and end with "Yakumo"). Recently, Blackberries and Windows Mobile devices were welcomed to the family. iSkoot currently works only on the Treo 650, and some Nokia and Motorola models.

Currently, I'm waiting for EQO's support staff to return my call for help. I tried signing up for the service, but my replacement phone isn't presently on the "supported models" list. Feel free to try it yourself, but remember to use your dummy e-mail when you do!