Generally, I agree that "none" is about appropriate - campus jobs are great for spending money (and you can't beat the hours - no evenings or weekends usually!).
I did not get an allowance while in college - I got a stipend from my scholarship, I had an on-campus job, and a part-time job at a doctor's office (I worked full time there during summers). It provided me with more than enough pocket money, plus enough to buy a car (that I still have 16 years later!). On the other hand, I lived at home, so my living expenses were zero. I bought my own gas and I bought groceries on occasion, but that was all in terms of cost of living (no rent, no utilities, etc.).
If it were my child and they were away from home (especially far away, like more than an hour or so), I'd want to make sure they at least had emergency access to $100 or so. But, I wouldn't be subsidizing their Friday night beer runs, KWIM? Maybe if you sent $50 a month regularly then a "surprise" amount some other times (or a gift card for gas, groceries, pizza, etc) as a bonus.