Snivellus

This reason for Dumbledore trusting Snape would be far superior than the lame excuse of, "His repentance was absolutely genuine when he heard about your parents."
Dumbledore wouldn't want to tell Harry about the time turner so he said that.

Maybe this has been discussed in this thread already, but remind me when it was exactly that Snape came to the Order's side (or falsely came to the Order's side--however you want to look at it), and the circumstances surrounding it. If you know where it happens in the books and could direct me too it that would be good too. I'm just (like everyone else) pondering what the reason could be for Dumbledore trusting Snape so much, and this would be very helpful in pondering that.

Maybe it was when Snape heard that Lily and James were dead and he 'repented' in front of Dumbledore. Maybe then he came over to the Orders side.

I'm pretty darn sure it says specifically in the books when it happened.

In book 4 in the Pensieve chapter Dumbledore says it before Voldemort's downfall that Snape came to their side. I'm guessing that there was a bit of time between him overhearing the prophecy in the Hog's Head and James and Lily dying. In that time Voldemort must have interpreted the prophecy as being about Harry, Snape heard about the interpretation and decided to become a spy.

I think that moment in book 4 is the best you're going to get.
Probably second best is that moment in book five when Dumbledore tells Harry all that Snape did that day, after Harry's "cryptic" message.
Bits and pieces all along, but nothing solid.

I always tht that Snape was on Dumbledore's side. (before reading DH, honestly!)

And i think it was a very very riskky job for Snape to act as Dumbledore's spy as well as to pretend tht he was on Voldy's side!!!

Absolutely! I mean, for Snape to have been able to look Voldemort straight in the eyes all the while being Dumbledore's spy!
Wow! Snape's one in a million......

I think that i always thought snape was good because dumbledore belived in him..and dumbledore is/was always right!! he knew that snape was someone worth trusting....and i think his guilt (snape's) was a big part of this...