A good place to start would be the library, if you're up for a bit of reading. Godric Gryffindor is the name of the wizard who founded our house. And then you can also ask the portraits and ghosts around the castle. Nearly Headless Nick would be more than happy to tell you about it. He's our house ghost, and he's quite friendly.
It's Peeves the Poltergeist you want to watch out for. He's a bit of a prankster, let's leave it at that.