UNLOCKING APPLICATIONS SOURCES

Cydia source: http://apt9.yellowsn0w.com/
Installer repo: http://i.yellowsn0w.com/

How to Unlock the iPhone 3G GUIDE
http://www.iclarified.com/entry/index.php?enid=2538

How to Jailbreak Your 2.x.x 3G iPhone Using QuickPwn (Windows)
http://www.iclarified.com/entry/index.php?enid=1881

IPHONE FIRMWARE 2.2.0 (3G)
http://appldnld.apple.com.edgesuite.net/content.info.apple.com/iPhone/061-5778.20081120.Aqw4R/iPhone1,2_2.2_5G77_Restore.ipsw

if not working for u try this

1.) Turn off your phone
2.) Turn on your phone
3.) Get off the SIM tray
4.) Wait a lil bit, and get it in
5.) Wait 1-2 minutes, if it don't work turn ON the AirPlane Mode, wait 30 seconds, turn the AirPlane Mode OFF. Wait a lil bit.

TESTED AND WORKING TRY AND ENJOY WITH YOUR IPHONE 3G