Just to put in my two pennies' worth...
I'm at Uni now, but spent a lot of time last summer working full time at Morrisons, and over last christmas as well. And I mean 39 hours a week of work, plus teabreaks, plus time to and from work... so basically work and sleeping and nowt else!
Anyway, I hated the jobs I had. They were generally physically hard, like collecting trollies out in the rain, stacking shelves, moving pallets around in the warehouse... they were also intellectually boring. Checkout work is horrible, easy enough to be boring but hard enough to let you make a serious mistake if yu lose concentration.
I got to know a lot of my colleagues, and I'm not insulting their intelligence or aptitude in any way- they did the jobs quicker and better than I did, we've just got different skills. Anyway, I knew several people there who'd gone straight from school at 16 or 18, and planned to spend some time there. I also got to know the older staff, who tended to take on the job just to get a bit more cash or whatever. Anyway, the way around that was that everyone spent as much time as they could having fun and trying to enjoy it, moaning for stress relief, generally complaining and most of all enjoying each other's company as a team. There's a lot to be said for having done a really depressing and horrible job with someone else, and being able to step back at the end of the day and think you did it together. Other than that, there's as many jokes and laughing and the odd prank as you want. All in all the thing that makes most really bad jobs tolerable is the people you work with!