Skype finally released their Skype application for iPhone. However, their app crashed every 30 seconds or so on my 2.2.1 jailbreaked phone, so googleing a bit led me to this post which pointed out that removing mobilesubstrate package could solve the problem.

Firing up Cydia and upgrading mobilesupstrate did the trick for me! So helloooo skype!

Should this not work for you, you can always fall-back to your beloved Fringe or Truphone!

Closing application will take you offline (imagine that!) so just leave it running and lock your phone. Or, you may want to try out Backgrounder app from Cydia.