The Dev team has just released the RedSnOw v0.9.6b1 to jailbreak iPhone 3G and iPod touch 3G running over iOS 4.1.
Also read Download Limera1n to Jailbreak iOS 4.0 and 4.1
Easy Steps to Jailbreak iPod Touch 3G and 4G with Limera1n
Jailbreak iPod Touch 3G and 4G with GreenpoisOn

Follow the simple and easy steps to jailbreak iPhone 3G and iPod touch 2G.
1) Download iOS 4.1 and RedSnOw 0.9.6b1.
2) Connect your iPhone 3G or iPod Touch 2G to iTunes and restore iOS 4.1
Note: If you upgrade iPhone 3G to iOS 4.1 then remember the baseband of your device will also be upgraded which could not be unlocked right now.
4) When your iDevice start running iOS 4.1, you have to execute downloaded RedSn0w 0.9.6b1.
5) On RedSn0w screen, click Browse button and select iOS 4.1 and click Next.
6) On next screen RedSn0w will provide many options, so select options according to your choice but this is must to select Install Cydia, so mark its check box and hit Next button.
7) Turn OFF your attached Phone 3G or iPod Touch 2G, keep it plugged-in and press Next button.
Now, RedSn0w will instruct to put your device to DFU mode, so follow the instructions carefully which would be displayed on RedSn0w screen.
9) When your device will enter to DFU mode successfully, RedSn0w will start jailbreak process.
10) When RedSn0w finishes jailbreak, it places Cydia icon on your iPhone 3G or iPod Touch 2G home screen.
Enjoy! You jailbreak iPhone 3G, iPod Touch 2G on iOS 4.1 successfully with RedSn0w.