Has anyone mentioned Half-Dwarves yet ? I've never understood why Half-Elves and Half-Orcs are so common but Half-Dwarves are virtually unheard of.
Another interesting option would be something similar to the Cursed from Ravenloft. Rather than a race unto themselves, however, it would probably work better as a template to be added to characters who have been warped by dark magics and transformed into something freakish, often while still in the womb. By creating a list of abilities to chose from, a player interested in creating a "Cursed" or "Tainted" character could choose to customize his freak as he or she saw fit. That way if someone wanted to play a Dwarven Hunchback with a vestigial tail and a club foot, or an anthropomorphic beast, or scaled monstrosity, they could.
Anyways, just thought I'd add my two cents.