I have used studentuniverse.com for both my trips to Europe. Once in 2005 with no problems and also for my upcoming trip this May. They are great. They do go to great pains to verify your student (or faculty) status so you can't fake it. They contact your school's itinerary or something. Totally painless.
The great thing about this website is my boyfriend and I had booked a flight from Amsterdam to London and the flight got cancelled. They called both of us, called the airline themselves to re-book us, and then notified us AGAIN (ie, called us back in 30 minutes or less) when they had achieved this.
I didn't think this site could get any better until the re-booked flight got cancelled AGAIN and they were quick to put us on another itinerary. No cost to either my boyfriend or myself. No hassles. No worries.
In January, we booked a flight from Los Angeles (LAX) to London (Heathrow) roundtrip + nonstop both ways on Virgin Airlines for about $550. Amazing! Non-student fares for that particular airline are often double that or more. I highly reccomend Virgin, by the way. They are great for an overseas flight (at least in my humble opinion).