Well, I am a big supporter of evolution, and have taken many classes on ancient geology and biology (I'm a sucker for dinosaurs
) I had this one class with a professor who was (for lack of bettter word) bigotted against Creationists. Like, serisouly, heh. We'd spend at least 15 min (of a 75 min class) with the prof litterally laughing at Creationists. So, weather I like it or not, I have sort of had it beaten into me that Evolution is the way to go.
As for there being no proof, I think that that is one of the weakest arguments for creationism. There are fossils that can be carbon dated back to millions of years, much longer then Creationists believe the world to have existed.
The fact that the earth is billions of years old also contradicts that it was created in six days, but I have heard an argument that "God days" are longer then "real" days, and I can even sort of buy that, being a spiritual person myself, but I still think that it is an excuse and flimsy at best.
Finally (for now probably) I also point to living fossils. The Coelcanth and other fish, not to mention Crocodiles and Sharks.
Creationism seems to me to be more of a hope that people cling to because it fits their personal dogma. Just a final Caveat, biogotted professor aside, I do want to insult anyone and if I have it was not intended. This is a subject I enjoy debating, though I doubt any creationists will change my mind, or me theirs.