I found the most fun site. It's called Fun Photo Box.
I won't tell you how much time I wasted on this site, but suffice to say, I could/should have been doing other things like tackling dish mountain and laundry mountain. It's really easy, just upload a pic - yourself or someone else and in the photo effects section plug it into one of the many choices they have. The results are super fun. The Harry Potter one would be great for a Harry Potter Party Invitation. I plugged the Eldest's pic into that one since he's the big fan:
And this one? Yeah, it's just part of my campaign to become famous: