I agree with Isis, in saying that Snape is on the good side. I mean after all if Dumbledore is such a wise wizard he would have had to have had a lot of trust in Snape, (despite how he may seem on the outside). I don't know but this is just my opinion. I believe that Dumbledore purposely appointed Snape as the D.A.D.A teacher in book 6 because he was planning for his (fake or real) death. The position of the D.A.D.A teacher has always been cursed since Voldemort placed the curse on it. Ever since then no teacher has lasted no more than a year. So why would Dumbledore have appointed Snape to that position without having a good reason to do so? At first I thought Dumbledore still possibly being alive was quite far fetched but I went on this site recently and there was some really interesting theories on Dumbledore's death on it, amongst other things. www.dumbledoreisnotdead.com check it out if you are curious
Music is everything...I want to hear the bass, the guitar the drums. I want to sway to your sweet rock'n roll and be forever lost in the beat.