Getting away from the chains.

You know what's in the price center and you've done the dining halls. Where else is can a hungry, broke grad student find some food on campus? What about the vegans and vegetarians? The wiki feels your pain, check out these places:

Global Cafe-just past the Warren Quad, and off the campus loop shuttle route you can find Vietnamese street sandwiches ($3.65!), pho, sushi and much more!
Mandeville Coffee Cart-tried and true the coffee cart had helped many a grad student in time of need. For people over by Warren Mall, Cups (by the stone bear) serves a similar purpose.
The Co-op in the old Student Center and the Co-Op Satellite in the Price Center. Great place for vegans and carnivores alike.
Hare Krishna lunch-only on Wednesdays but lots of food for $3.50! 11a-2p on the roof the Original Students Center
International Center lunches-every friday cuisine from a different country is featured at the International Center. Just $4 a plate.
Be on the look out for free food on campus. Sometimes those emails crowding your inbox contain precious info about free food. Look especially at the "all-grad relay" grad announcements that come through every week.
Faculty Club: lunch only, but an all you can eat buffet, menu changing every day http://facclub.ucsd.edu. Any graduate student can become a member. There is a registration fee, but usually during the Fall quarter either it can be waived or there is a discount.