Read the whole post before proceeding. If confused or need help locating a particular custom firmware file, please send me a Private Message (click me!)
There's a custom (PwnageTool) firmware depot located at the domain cfw.ailypso.com. I can't directly link the IPSW firmwares, so let me tell you how to find the IPSW you're looking for by telling you how to look. Underscores separate all values after the .com.
If you're confused, look at the nomenclature of Apple's firmwares at Firmware. - The iPhone Wiki. Version and build numbers can be found there as well.
PLEASE NOTE ALL CUSTOM FIRMWARES NEED CORRESPONDING SHSH BLOBS FOR YOUR iPHONE UNLESS OTHERWISE NOTED OR TOLD!
As of 6 Dec. 2010, all IPSWs version 4.1 and lower are untethered jailbreaks. 4.2.1 and higher are tethered unless otherwise noted.
The first part of an IPSW after the ".com/" is the iPhone model, as defined in the normal IPSW. There is no underscore between the .com/ and the model number.
The second part of an IPSW is the version number of iOS the file is made from.
The third part of an IPSW is the build number of iOS used to make the custom file.
The fourth part refers to whether or not the IPSW is already "activated" or is "unactivated" and will require an authorized carrier's SIM card to activate (or SAM). iPod touches and iPads will have this section replaced with a simple "pt" instead.
The fifth part refers to whether or not there's a baseband update contained in the IPSW. If there is, the IPSW will read "bbupdatexxxxxx" where the x's represent the installed alpha-numeric baseband version without any periods or underscrores. An IPSW with "nobbupdate" will be marked as such. iPod touches and iPads will have this section omitted.
The sixth part applies only to iPhone 3GS and iPod touch 2nd generation files. They will be marked with as either "newrom" or "oldrom" depending on whether or not they are made for an old-bootrom device or a new one.
A "tethered" or "untethered" will be added, if different from the norm for that version, will be noted following bootrom type. If the IPSW follows the norm (e.g., an always-untethered 4.1 version) this field will be omitted.
Any file that needs no SHSH blobs will be marked "noshsh" at the very end of the IPSW, otherwise (normally, almost always) omitted. Any file that requires SHSH blobs for a version OTHER than the installed version (e.g., a 4.2.1 version requiring 4.1 SHSH blobs) will be marked xxxshsh with the x's replaced by the version number.
All IPSW files have a .ipsw immediately following the last part, with no underscore between the final part and the file extension.
A file with specific verification and legal information (exact size, hash digests, copyright information) will be found with the exact same name but with .txt replacing the .ipsw at the end of the URL.
Some examples could be (not actual links):
/iPhone2,1_5.1.3_9E18_unactivated_nobbupdate_newrom _untethered_41shsh.ipsw
/iPod4,1_4.2.3_8D11_pt_41shsh.ipsw
/iPad1,1_4.6.1_8G561_pt_nobbupdate_tethered_noshsh. ipsw
Happy hunting!
EDIT: Currently only IPSWs for unactivated, no baseband update iPhones for 4.1 and 4.2.1 are in the depot.
A good idea, but sorry to say I couldn't find anything -- and I'm not drunk (haha .
Maybe have all options for all files. Or maybe you could enable the web server dir option and see a list. Not sure if that would be acceptable MMI policy.
I apologize for making this seem so convoluted. Regrettably, I have to obfuscate it fairly heavily in order to comply with the "no directly linking to custom firmware" rule.
Perhaps I'll make it clearer to PM me if you can't find your firmware in the OP--that's legal.