This could be a really neat little site for any Tolkien fan to check out. I found it a bit slow loading, but it's so comprehensive, that the wait is well worth it. The site, The Lord of the Rings Project is a family tree of everyone from the Valar and the Maiar to the various families of the Elves and the Houses of Men, from the creation of Arda all the way through to the end of the Return of the King.
Or, at least it's supposed to have. To be fair, this is still a work in progress. I'm not seeing any of the hobbits yet, for example, but all of the houses of Men are there, as are the Rohirrim royal family trees etc. I think it'll just take some more time.
I do know that I'm going to be checking back every now and again to see how things are progressing.