Sn0wbreeze 3.1.3 V1.5 has been released which adds support for iPod touch 2G (older non-MC model).
Follow the complete step by step guide posted here to jailbreak your iPhone and iPod touch using sn0wbreeze 3.1.3 V1.5. Once you are done with jailbreak, you can then unlock your iPhone 3G and 3GS using ultrasn0w or blacksn0w.

I would strongly suggest iPhone 3GS users to stay away from this release as this release like all previous versions sends iPhone 3GS into an infinite loop after first reboot. If you have a Mac, I will strongly suggest you to use Dev-Team’s PwnageTool 3.1.5 which can jailbreak iPhone 2G, 3G, 3GS (older bootrom and with baseband 04.26.08).

Download .NET Framework 3.5 (required to run Sn0wbreeze)
Download Sn0wbreeze for Windows
source