I agree with Clare. $50 is a lot of money! For my son's friends who graduated this year, his very good friends, we gave a stand-up photo album with pics of the guys together over the years and $30 in an envelope. It totalled about $50 anyway. But this gift was for friends who literally have lived at my house for years.
My son received from friends: $50 to Best Buy, a Sensa (@ $50) pen, $30 to Best Buy and a Flat screen TV/DVD Combo with a check for $100 in the card. That family happens to be extremely wealthy!
Ideas that I like and that seem reasonable are: photo frame to take to college, a decent pen, a fancy make-up bag or a book. I bought several books called something like "Things I Wish I'd Known Before Starting College" with info from college students about the in's and out's of college life. These were gifts for "lesser" friends who we wanted to congratulate. Hope that helps, Alexis