The following is a user-submitted list of PCB manufacturers. Your results may vary.
2.50 / square inch, must use your own software to generate Gerber files. Easy-to-use web ordering interface, but slow turnaround time -- 10-20 days. Boards come out very nice -- precut, double-sided with silk screen and solder mask on both side.
Good online design rule checking, easy web ordering interface, and small standard trace/space tolerances. Students can order single PCB's for $33 each.
Bulgarian PCB manufacturer - $33 for a 6.3" by 3.9" board. I.E. cheaper than BatchPCB, but with a minimum board size requirement, silkscreen on one side only, and a more complicated ordering process.
Offers their own free (proprietary) schematic and PCB layout software -- easy to use, but you are locked into using their service. Integration with ordering system simplifies the process of ordering boards.