I don't know at all if this was recced on crack_broom or not, but I'll give it a shot. It's "1234" and has both Sirius/Remus and James/Lily. Bonuses include a young Gary Oldman and young David Thewlis!

...okay, I just found this one now, by the same person: "Don't Stop Me Now". THE EDITING. THEY MAKE ALL THE SIGNIFICANT LOOKS THEY MAKE IN CANON.

These are fairly old vids, so if you've seen them already, I apologize. XD