If you typically send patches to mail lists then Felipe Contreras' git send-email tricks blog post is definitely worth reading.
In a discussion on creating a git repo for the gcc code base, Linus describes how git uses delta chains and how they relate to packing.
In the same discussion Linus has additional low level explanation.
Zach Rusin has created a very easy on the eyes git cheat sheet. This is very useful if you use some git commands only once in a blue moon.
I finally ran into a firewall issue in that I could not gain access to a git repository that was only available using the git protocol.
I knew how to setup OpenSSH to be a SOCKS proxy, so I needed a way to get git to use a SOCKS proxy.
Works great!
Linux Magazine has an excellent article, Embracing the Git Index, that demonstrates how git's index is used.
kernel.org hosts gitweb that is an excellent interface for browsing kernel code changes changes.
You can even track the stable kernel queue.
If you have git and plucker installed, then you can easily create a Plucker version of the git documentation for you Palm.
plucker-build --title="git" --doc-name="git" --doc-file="git" --stayonhost="" --maxdepth=10 file:///usr/share/doc/git-core-x.y.z/git.html
For the lazy among us, here is git.pdb.
Update 2009-10-11: Removed git.pdb because git documentation has been updated significantly since I created this plucker document. Also, I no longer use a Palm device so plucker is not an application I use anymore.
git supports applying tags to the HEAD, but is not so easy to check out a specific tag. See the LinuxMips wiki for a description of how to check out a tagged release.
Fedora Extras is keeping up to date with new releases of git so now I can take a stab at figuring out how git works.
On a Fedora system, start with /usr/share/doc/git-core-x.y.z/core-tutorial.html.