Search And Destroy on tth (author/link unavailable atm) is an IntegraHellsing!Buffy story that seemed like it was going very well, but just kindof stops.
Another Kind of Angel (?) also on tth is a Walters(?)!Xander that has Xander joining the Hellsing operation in Europe. Enjoyable, if a little frustrating with the relationship tangles.
Considering I've never really seen or read any stories about Hellsing, the way the author did these crossovers is actually really good.
I saw a one shot with TatewakiKuno!Xander that was entertaining. I believe I saw it on ff.net.
Does anyone know of a Ranma!Willow or maybe Shampoo!(Scooby) or any other Ranma 1/2 YAFHs?