To borrow a line from Sexy Sev himself...

No-one? How disappointing.

Out of The Depths from Fanfiction.net

but you can search "Out of the Depths fanfic" in google to see it easier. :)

cheers!

Lol, I know some good ones but they're HG/SS. Perhaps if you put this question up on the Severus Snape & original female charactes fan group

link

Well, I have one.

While it's not about Snape, but the main character is Snape's favorite student.

Interested? See my profile at June!

Well,
link is an awesome one (;))

link

And, since FF.net has been so wonky, I've been searching the net and stumbled across two forums for Severus/OC pairings. Most of the stories here are pretty good:

link

and

link

Try frd24906 on deviantart. Posted in 3 parts. The title is A Kiss To Remember.

You might try finding LadyNottingham on here. She writes some excellent fanfiction with our favorite Severus Snape and OC characters. Think her profile has a link to her fanfiction.net page.

Thanks to everyone who responded! I have actually stumbled across several wonderful SS/OC fics myself on fanfiction.net and a few others fic sites. Now I'm currently following several great Severus fics and have been working my way through some completed fics as well. I posted the links to 2 SS/OC fics on the Severus Snape & Original Female Character fan wall and and will add some more. If this pairing interests you, go check them out! (As a side note, I also found 2 awesome Die Hard Hans Gruber/OC fics and posted links on the Hans Gruber fan wall. Still searching for any decent Sheriff of Notthingham and Colonel Brandon fics though....)

Just an idea (it's a long one, mind: covers the biggest part of OoP, HBP and DH) : link.