I'll start off with this one: If Snape died on May the 2nd 1998, what's he doing here in 2001 in Snape magazine!

Sorce: link

Here's another one: On January 2006 "Eagle eyed users of the satellite imaging service Google Earth have spotted what appears to be a car hovering above the ground in a suburban Perth car park."

If you look in the black square, that's clearly Snape in his black robes casting a levitation spell on the white car!

Proof again that he did not die in 1998 and was either visiting or is living in Perth, Australia.

Sources: link and link

:) I got another one: A possible sighting of the professor himself!

Hannah Goldfield from link has reported seeing "...a man inexplicably dressed as the Harry Potter character Severus Snape" on Thursday the 22nd of this month while waiting in line for the midnight screening of “The Hunger Games” at the UA Court Street theatre in Brooklyn.

Yet more proof the professor survived that nasty, nasty snake attack!

I work two jobs, and my second job is at a food joint. One afternoon while I was stocking the veggies, I looked up and there before me was a yong man who could have been a great body-double for Our Potions Master. I very nearly fainted.

^ I would have probably found myself following him for a little bit until either I or he realised I was subconsciously stalking him and then promptly die of mortification :P

Hey, I just wanted to run my fingers through his hair... and kiss him a little. :p

<.< >.> Nothing wrong with that...

During this past school year, I occasionally volunteered at the school store, which is open for 15 min before the late bell. Anyway, there was a kid, either in 4th or 5th grade, who could have played young Severus. He had the pale skin, long shaggy dark hair, pre-teen gothy clothing. It's as if he walked out of central casting. The first time I saw him I almost dropped the school supplies!

Cool, I guess we could go with the whole de-aging potion/spell angle on that sighting... or maybe reincarnation?... though that would need for him to be dead, so probably not! We'll go with the de-aging theory :P