Package containing the adb and fastboot binaries and a handful of simple shell scripts to drop them into the appropriate places on mac / linux. Nice.
Really useful guide on how to unock and root the Nexus S. Easy enough to follow, and it actually works!
A list of ROM packages for the Nexus S, migrated from the xda-developers forum.
A list of ROM packages for the Nexus S, the post says it has been migrated to a new location on a blog.
A Windows desktop client that allows downloading from the Android market. Requires Google username / password and some other data that appears to be sniffed off the device.
Step by step instructions on how to flash the rom of the Nexus One. Only missing part is the udev rules for Ubuntu.
I downloaded fastboot from this page for the HTC Google Nexus One.