Well, I would recommend getting a hamster mix food at your pet store to have as a staple food. But things like bits of apple and banana and pineapple are good, so are raw spinach, lettuce, cabbage, cucumbers, carrots...pretty much any fruit or veggie you could eat raw. I don't reccomend apple seeds or canned peaches because they can contain trace amounts of cyanide, not in any amount to hurt you, but it could make your little friend sick.
But hamsters love seeds and fresh veggies! Sunflower seeds make awesome treats, but they have a lot of fat so use sparingly. ...My hamster doesn't want to eat much else, but I give him lots of excersize in his little ball and he has a really cool wheel that not only spins but rolls around in a circle, too. :-D Have fun!