well there's this wonderful new classification of crossover on ff.net now :

24 are listed; I'm sure a few aren't, but you might be able to find them with the "search" tool:

http://www.fanfiction.net/Dark_Angel_and_Supernatural_Crossovers/467/2237/10/0/1/1/0/0/0/0/0/0/1/

and yeah, I know some aren't great. The ones I really liked are :

Run Away: Max gets picked up by the Winchesters when she runs away from Manticore. This one is SO good I read it a couple of times.

Insane Troll Logic's verse is EPIC, but it can be found on LJ too so I don't know if you've read it yet

That's about it for the ones I can remember :)

Also one of my favorites on LJ: Mistaken Identities: http://mellaithwen.livejournal.com/70827.html