Well, he's a student, so he shouldn't be pushing the limits, or at least not producing a design that is pushing the limits!
For small boards, oshpark.com is well regarded, but can get costly quickly at $5 per square inch for three boards.
For larger boards, I like itead studio, but beware of getting close to their minimums. I just ordered some 2x3" boards - $14.90 plus shipping for 10 of them - about $22 total.
Personally, I like to set my minimum spacings and trace widths to what some would consider ridiculously high. That way, I can produce a board myself using the MG Chemicals photographic process in an hour or so. But then you need to be able to print transparencies and need a UV lamp to expose the board. Double sided boards are doable, but you don't get plated through holes and soldering wires in for vias gets tedious, so I use oshpark or itead studio for anything more complicated.
I would stay away from any PCB producer that makes you use their own software if you ever want to sell the board or give the design away. These producers charge a premium and your 'customers' will not like paying it. (I paid something ridiculous like $300 for one design published in the ARRL Handbook that used such a producer.)