I've printed all of my covers for 28mm cases at Kinko's, and since running into a snag on my own printer have started printing my 14mm and DS cases there as well.
Always at a self-service machine (the pro one, 'cause it's the only one with Adobe PS and the times I've tried to print outside of Photoshop, the results weren't correct) -- actually the first time I tried to have them print them, but the guy couldn't figure out how to print in landscape on legal paper, so he let me try (on their setup, behind the counter) and then I got yelled at by a different Kinko's employee for being behind the counter, and he told me to go to the self service machines.
Only problem with the self service machines (and specifically the pro ones) is, in addition to paying $.99 a color print (same price for regular or legal paper), you also pay a per minute price (and it's double on the pro machines from the regular ones).
A tip if you'd like to avoid the Kinko's staff peeking over your shoulder all the time; if you have a 24hour Kinkos, go in around 11 on a Thursday, Friday or Saturday night and it's usually dead iwth 1 employee working (who's typically working on overnight orders that need to be finished for early morning pickup and thus will ask if you need help and then leave ya alone). If you go in during busier hours, they've got more staff and usually have at least 1 staff who walks around to "assist" (or in the one case I went at 5:30pm on a monday... annoy the hell out of you by treating you like an idiot who has no idea whatsoever of what your doing).