Yep, right now I'm using Soundcloud and following a user on there who frequently posts new sets from popular artists. But it's just one user; I'd love to see that concept expanded upon and taken to a new site entirely. This site has been bookmarked; I'll be tracking to see where this goes!
This is way beyond essential mixes . . . I haven't come across one good dj mix sharing website out there.
Linking to already hosted content is 100% the way to go.
Please keep it going.