Why is Git not found after installing OS X Lion?
If /usr/local/git already exists, you'll need to either add it to your $PATH or make a symlink placing the symlink inside a directory that is in your existing PATH.

A common practice is to make /usr/local/bin if it doesn't exist and add a link:

sudo -s
mkdir -p /usr/local/bin
ln -s /usr/local/git/bin/git /usr/local/bin/git
exit