A quick note about firmware: The firmware of the iPod Touch/iPhone is essentially the OS.Apple has released 10 iPod Touch/iPhone firmware versions: 1.0.0, 1.0.1, 1.0.2, 1.1.1, 1.1.2,1.1.3,1.1.4,2.0,2.0.1,2.0.2 and 2.1. To find out which version you have, in your iPod Touch/iPhone go to Settings>General>About>Version. There you will see your firmware version.
iPhone Firmwares:
v1.0.0 --> herev1.0.1 --> here
v1.0.2 --> here
v1.1.1 --> here
v1.1.2 --> here
v1.1.3 --> here
v1.1.4 --> here
2.0 (3G iPhone)--> here
2.0 (EDGE iPhone)--> here
2.0.1 (3G iPhone)--> here
2.0.1 (EDGE iPhone)--> here
2.0.2 (3G iPhone)--> here
2.0.2 (EDGE iPhone)--> here
2.1 (3G iPhone)--> here
2.1 (EDGE iPhone)--> here
2.2 (3G iPhone)--> here
2.2.1 (3G iPhone)--> here
2.2.1 (EDGE iPhone)--> here
iPod Touch 1st Gen Firmwares
1.1.1: here
1.1.2: here
1.1.3: here
1.1.4: here
1.1.5: here
2.0: here
2.0.1: here
2.0.2 : here
2.2.1 : here
iPod Touch 2nd Gen Firmwares
2.2.1 : here
Note : Do not try to use 1.0.0, 1.0.1, 1.0.2 to iPod Touch or you will mess it up!!Trust me!!