Update: The iPhone Dev Team have updated Redsn0w to 0.7.2 – Download the newest version from our iPhone Downloads section:
redsn0w 0.7.2 for Mac OS X download
redsn0w 0.7.2 for Windows download

iPhone Dev Team has released an application that works similar to quickpwn and provides similar functionality. Redsn0w is an easy to use, multi-platform, multi-device jailbreaking and unlocking (iPhone 2G only) tool for the iPhone 2G (original iPhone), the iPhone 3G (but not the 3GS) and also the iPod touch (first and second generation). Luckily for Windows users, who couldn’t use PwnageTool, Redsn0w is available for both Windows and Mac OS X users. However, iPhone Dev Team notes that there are some issues using redsn0w with OS X PPC and they suggest you use an Intel Mac till these issues are resolved.

1. GOLDEN RULE: If you are using a 3G iPhone with yellowsn0w and rely on yellowsn0w to obtain cellular service, then you should NOT use redsn0w right now. Ultrasn0w (the 3G carrier unlock) is not included with this release and therefore your baseband will be locked and unable to use an operator other than the official one it was bought for. UltraSn0w will be released via APT (cydia and icy) soon. If you have an original iPhone (1st generation) then 3.0 carrier unlock works with this redsn0w release.
2. Yellowsn0w in its current form will NOT work with the baseband version that is present in the 3.0 update, you will need Ultrasn0w, which will be released sometime soon, Ultrasn0w will work with all iPhone 3G models (but not 3GS), even ones that were previously unlockable, Ultrasn0w (when available) will be released via APT (this means you will be able to get it via Cydia or Icy).
3. Please read all parts of this post before downloading and using these tools.
4. Read items 1, 2 and 3 again and again.
5. This app is suitable for the recent 3.0 release
6. redsn0w will NOT work for the iPhone 3GS.
7. redsn0w WILL work for Original iPhone (1st Generation), Original iPod touch, iPod touch 2G and the iPhone 3G (not the iPhone 3GS).

Redsn0w is easy to use, simply upgrade the device in iTunes to firmware version 3.0 and run redsn0w to activate and jailbreak the device (and if you are using an original iPhone 2G, it will unlock it too!)

Redsn0w download:
redsn0w for windows download
redsn0w for Mac OS X download

*Note*: there are some issues using redsn0w with OS X PPC, please use an Intel Mac while the iPhone Dev Team fixes these issues

- source: blog.iphone-dev.org

Today, the famous and very well known iPhone Dev Team have released their long awaited iPhone OS 3.0 jailbreak for both iPhone and iPod Touch. Sadly for Windows users, PwnageTool is Mac OS X only, but Quickpwn for Mac OS X and Windows will be released very soon according to the iPhone Dev Team.

1. GOLDEN RULE: If you are using a 3G iPhone with yellowsn0w and rely on yellowsn0w to obtain cellular service, then you should NOT use PwnageTool right now. UltraSn0w is not included with this release and therefore your baseband will be locked and unable to use an operator other than the official one it was bought for. UltraSn0w will be release via APT (cydia and icy) soon. If you have an original iPhone (1st generation) then 3.0 unlock works with this PwnageTool release.
2. Yellowsn0w in its current form will NOT work with the baseband version that is present in the 3.0 update, you will need Ultrasn0w, which will be released sometime soon, Ultrasn0w will work with all iPhone 3G models (but not 3GS), even ones that were previously unlockable, Ultrasn0w (when available) will be released via APT (this means you can get it via Cydia or Icy).
3. Please read all parts of this post before downloading and using these tools.
4. Read items 1, 2 and 3 again and again.
5. This app is suitable for the recent 3.0 release.
6. PwnageTool will NOT work for the iPhone 3GS.
7. PwnageTool WILL work for Original iPhone (1st Generation), Original iPod touch (1st Generation) and the iPhone 3G.

SIM Free/SP Unlocked/Factory Unlocked iPhone 3G

This applies if you bought your iPhone 3G for $$$$$$$. This model of iPhone 3G doesn’t have an Service Provider lock (aka factory unlocked) and you are able to put any SIM card into the phone and get service. Your phone is already unlocked so you do not need to worry about baseband updates, simply upgrade to 3.0 using iTunes and then use PwnageTool to create an ipsw and then use this to jailbreak your phone.

iPhone 2G (1st Generation)

Use PwnageTool to do the magic and then restore with iTunes using your newly created .ipsw ‘nuff said, you don’t need to worry about anything, the baseband will be unlocked, the phone jailbroken.

iPod Touch 1G (Original iPod Touch)

Use PwnageTool to create a firmware image and restore with that .ipsw using iTunes.

iPod Touch 2G (New iPod Touch)

Sorry, no support at this time within PwnageTool, use Redsn0w for an earlier (pre 3.0) firmware release instead.

Download:
PwnageTool version 3.0 Download

- source: blog.iphone-dev.org