Something joint with the local alum association is a good idea - get the alums to make them dinner! The alums like it because it gets the new graduates interested in staying involved, and hey, it's a free meal for hungry college students.
For a gift, I personally like the idea of using a recognition Quill. They aren't that pricey and are something alums can wear all the time. When you're graduating, the last thing you need is yet another t-shirt. You can also give pin boxes, scrapbooks - anything AXD that the alum will cherish and find a use for post-college.