I did Google it. I only found one. SIPDroid, but I haven't found any credible source that it works with Skype contacts, and searching here for VoIP didn't work well.
Twoo, is there a good reason you are being such a jerk? I am all for people using search features but come on!
As for the OP question, Google Voice provides you with a phone number that people can call and you decide which of your phones it will ring to. If you go to the site voice.google.com it has some great videos explaining the full service.