I'm spending some time updating my Rails projects to use Capistrano 2 and Git. Here are the steps I took to build Git on my Ubuntu 6.06 slice.
sudo apt-get install curl libcurl3-gnutls-dev libexpat1-dev
wget http://kernel.org/pub/software/scm/git/git-1.5.4.5.tar.gz
tar xvf git-1.5.4.5.tar.gz
cd git-1.5.4.5.tar.gz
NO_TCLTK=yes make prefix=/usr/local all
NO_TCLTK=yes sudo make prefix=/usr/local install