I came to the world of fan fiction, because I had a theory about Snape... and I decided I wanted to actually see it, to make it come alive. And thus was born The Secret Papers of Regulus Black.
That story has remained, in a way, a home base for me, and I have returned to it to write a sequel (currently in progress) and two prequels. The prequel I wrote first is still waiting to be edited. The other one, which happens earlier in the storyline, is Damage Control. Both of those were written early this spring.
After writing The Secret Papers of Regulus Black, I changed focus and began work on a highly self-indulgent work of plagiarism that will never see the light of day (and I do only work on it at night :) ), because despite the irresistable urge to work on it, I do respect the original author. This was my first Hermione/Snape, which naturally affected the next thing I started: the sequel to Papers, mentioned above. I got distracted at the Mugglenet forums, and wrote a challenge piece: The Labyrinth of Lost Souls. It won second place in the Gauntlet Challenge. At this point in time, it's only up there, since it was their challenge.
One of the things in the challege was a logic problem, and it sparked another idea, The Logic Problem. I also have a work in progress for the HG/SS exchange. It's not doing so well. The beginning is boring and is taking too long. I'm several chapters in, and we're still at the Weasleys'!
Finally, for NaNoWriMo, I wrote a 117,000 word work about what would happen if a Muggleborn rights group became as extreme as Voldemort's Death Eaters... only in favor of Muggle-borns instead of Purebloods. I'm currently working on editing it, after which, I will send it to my beta. All of my stories feature Snape as a main character (sometimes the only main character). I tried writing a Draco story, but it fell rather flat.
I am very interested in his (non-romantic) relationship with Dumbledore, and at some point, I will probably write something about why and how Snape joined and left the Death Eaters. It will in all likelihood feature more of Regulus Black than Lily Evans, and it will probably be connected to the Papers series.
Of course, that's not the next story I will work on. I have two stories about different possibilities for Year 7. One of them is very dark, and is set in a world where Voldemort has managed to take over the Ministry and Hogwarts. The other one supposes that Snape is supposed to still spy, and needs someone who can get Horcrux information to Harry without telling every member of the Order where Snape's true loyalties are. Both of those are Snape/Hermione stories.