Blackra1n 3.1.2 05.11.07

Assuming you are on baseband 05.11.07 and 3.1.2 you can use blackra1n to jailbreak.

HOWEVER

You will need to use blackra1n to boot your blower _every_ time.... Not a problem if you never run out of battery, or always have a pc with you.

You can always use iTunes to restore if you get annoyed with all of this, so as long as you are all backed up, no problemo.

You will need:
1 x blackra1n
1 x iPhone
1 x Mac (Intel)

Goto http://blackra1n.com, download the mac version.

--- THIS IS THE BOOT PROCESS YOU HAVE TO FOLLOW EVERY TIME ---
Make sure iTunes & iTunes helper are NOT running:
Properly close iTunes(right click, quit), then open a terminal and type:
ps -A | grep iTunes
You will see the id of the process running iTunes helper (1st col). Type:
kill 186
Where 186 is the process ID
Then, plug in your iphone, run blackra1n and press "Make it ra1n"
Your phone will reboot and a lovely piccy will show up
Done!
--- END OF BOOT PROCESS ---

You then have blackra1n as an app, use this to install Cydia (the unofficial app store)

Thanks goes to Geohot