Its not free or a website but for about �25/�30 Family Tree Maker 2006 Deluxe software is fantastic. I've been doing my tree for a few years and my mum bought me this package for Xmas.
You can easily add and delete people, put in any number of dates, images, notes, facts about anything you want.
You can also print many different types, views or branches of your tree
It comes with a free 90 day subscription to Ancestry.com, 3 Parish Records CDs, Scottish Parish Records CD and the 1851 census sample (10% of UK population shown)
I would highly recommend it - well worth the small price. Shop around on the net to get a good price too.