There is a very manual tutorial up at xpwn.co.uk on how to Jailbreak your iPhone with the 2.1 firmware:
T14:19 <+geeb> http://xpwn.co.uk/2.1JBtut.txt
14:19 <+geeb> 2.1 3g jailbreak tutorial
14:22 < comm> geeb: has it been tested?
14:22 <+geeb> comm
14:22 <+geeb> yes by me
14:22 <+geeb> and others in #xpwn are running it now
The following are the instructions
Download the 2.1 firmware <--http://appldnld.apple.com.edgesuite.net/content.info.apple.com/iPhone/061-5198.20080909.K3294/iPhone1,2_2.1_5F136_Restore.ipsw install itunes v8 (http://www.filehippo.com/download_itunes/) <-- all versions of itunes are there Update the iphone with iTunes and make sure it is activated! Uninstall iTunes v8 Uninstall Apple Mobile Device Support (From Add/Remove Programs in Control Panel) Install itunes v7.7.* Download quickpwn with the correct 2.1 bundle inside it http://xpwn.co.uk/quickpwn-gui-for-2.1.rar Run quickpwn...select your iPhone1,2_2.1_5F136_Restore.ipsw you can select cydia and installer and logos if you wish When it is finished the phone will reboot...Cydia and Installer will NOT be visible Download TotalCommander <-- http://xpwn.co.uk/tcmd704a.exe Download t-pot addon <-- http://xpwn.co.uk/T-PoT.1.1.zip Install TotalCommander and in the left pane navigate to T-PoT.1.1.zip and click on it. It will install t-pot automatically. Download the mobileinstallation patch <-- http://www.sendspace.com/file/pcrxy6 Use Totalcommander to install patched mobileinstallation to /System/Library/PrivateFrameWorks/MobileInstallation.framework ... clickon the dropdown box top left and select network neighbourhood then t-pot. Still in TotalCommander delete /private/var/mobile/Library/Caches/com.apple.mobile.installation.plist Reboot the phone and all is good! Thanks to the #xpwn crew...