When I was in college I had about $100 a week to do what I pleased. I worked on campus and my parents gave me $20 when I visited. That was usually more than enough for me to go out and do as I pleased. On a normal basis, I would have a little extra every week. Sometimes I'd spend my extra cash on something on eBay or something to treat myself. Some of my friends spent more than $100, but even more friends spent less - and they all survived!
Here is a site with Student Budget Plans that Work. This was actually just recommended to me by a friend. Check it out.
But, it also depends on where you live. Depending on where you live, movies, concerts, bars, etc. all cost different amounts. So, make sure you gauge that in.
Some sound advice, if you can survive on less, save your extra cash. Throw it in a lock box or even open up a savings account. Just in case your friends want to go on a trip or there is something you REALLY want, you have a stash of cash waiting for you. This is something I wish I would have done. Learn from my mistake!