I dare say that this thread should be stickied and more sites should be added when found.
Although
http://lucy.allakhazam.com/ is filled with new content you can click on history to see what spells and items used to be like before they were changed. The changes only go back as far as 2002 but it's better than nothing.
For example, a bunch of changes where made to spell levels in 2005 so you can see the original level on Lucy. Same goes for items.