In this I am not trying to show how that git and hg are the same. I only want to show how common tasks could be done in the two versioning systems. Please be aware that (as some commented) this might create confusion, since there is no 100% same way to do things and branches, tags and whatever do not always have the same meaning in both worlds. So please be careful. I find the cheatsheet useful, so might others
Discussion ongoing in the comments section.
--- update 1: Wed Mar 9 11:22:54 CET 2011