http://stackoverflow.com/questions/35837/what-is-the-difference-between-mercurial-and-git thread on stackoverflow that contains several useful links comparing git and hg (mercurial)
http://progit.org/book/ excellent git reference book, read it even if you are already familiar with git
http://gitcasts.com/ screen casts tutorials for basic git usage
http://www-cs-students.stanford.edu/~blynn/gitmagic/ Good article that explain basic version control tasks and how to do them with git. Other git how-to articles start with how git differs from other vcs’es and explain about git internals and by doing that they create a huge deal of confusion.