download from here ;

Dev-Team Blog - Untethered holidays

https://sites.google.com/a/iphone-de...directs=0&d= 1

or
Updates #5b and #5c: Version b5b fixes an issue with using custom ramdisks on iPhone3G and iPod2G, and version b5c prevents redsn0w from crashing due to the ever-growing ramdisk size.

TIP: If auto-detection fails and redsn0w tells you no identifying data was found, you can always pre-select the appropriate 5.0.1 IPSW using “Extras->Select IPSW”.
Here are the redsn0w download links: