Alright - I'm just going to throw this out there regarding what I have found -
Free T-Zones on prepaid (no sidekick plan stuff):
= Unlimited free skype messaging (you can even call, but there is a delay)
= Can sign in to Google voice - haven't really tried doing anything
= Access to Yahoo! mobile - yahoo mail, movie times, etc
= Access to mobile news sites - BBC (no one tells you about this one), CNN, EPSN....

I'm sure there is more...

This is all for free - no daily charge or anything - buy your $10 prepaid card (which comes with $3 of credit) and you can do these things all you like.