As noted in this thread,
the untethered exploit was not patched. When 4.3.3 was first released,
there were some kernel crashes and other related issues that kept these
above programs from rendering an untethered jailbreak. PwnageTool,
redsn0w, snowbreeze & ultrasn0w were updated for 4.3.3 Untethered
jailbreak. So if you have an iDevice on 4.3.3, whether you accidentally
updated or not, you can now jailbreak it.
*Snowbreeze also works for the 4.2.8 iOS on verizon iPhone.
redsn0w for OSX
redsn0w for Windows
PwnageTool - Torrent
sn0wbreeze
Ultrasnow is available through Cydia. If you don't already have it, the repo is: repo666.ultrasn0w.com
If we aren't allowed to post torrent links, please tell me, and I will remove it. I'm not sure if they are allowed or not.
The following is copy/pasted and is if you wish to unlock your iPhone on 4.3.3
To unlock an iOS 4.3.3 device, use the ultrasn0w tool. Remember that
ultrasn0w at the time of this writing only worked with iPhone 4 baseband
1.59.00 and iPhone 3G/3GS basebands 4.26.08, 5.11.07, 5.12.01, 5.13.04
and 6.15.00. Use a custom IPSW to update to 4.3.3 in order to avoid
updating your baseband. You may wanna use excellent ipswDownloader for
Mac to easily find and download any iOS firmware build. This app also
figures out your baseband version and tells you whether your iOS version
can be jailbroken and unlocked. If you’re on Windows, download the
f0recast app that checks whether your device is unlockable or tethered
with a USB connect.
EDIT: I've updated the Redsn0w download links for the new version released, rc16, which is supposed to fix battery drain.
Source
Source 2