Ultrasnow 0.93 is compatible with all basebands since iOS 3.0, they include, 04.26.08, 05.11.07, 05.12.01, and 05.13.04. This only works with phones that were previously jailbroken. This worked for me (I accidentally upgraded my phone to 3.1.3 with 05.12.01 baseband).
How To Jailbreak iPhone, iPod Touch Using Spirit For iPhone OS 3.1.3, iPhone OS 3.1.2 [Windows]
Jailbreak iPhone 3.1.2 Firmware with blackra1n (see link above for better way)
Jailbreak iPhone 3.1.2 Firmware with blackra1n (see link above for better way)
Browse Flash Websites on your iPhone and iPad [No Jailbreak Req.]
gv mobile is free and makes free calls
(with iphone jailbreak)
icall is free
vonage on iphone is free and makes free calls
http://www.youtube.com/watch? v=o5kZoniTFEE
http://www.youtube.com/watch?
skype to skype is free
skype free to residential/biz