Depends if its a mental or psychical job really
Are you willing to be fun/silly?
http://uk.answers.yahoo.com/question/index?qid=20060620064232AAaA1Oz
This made me laugh, the top answer.
Otherwise:
Do not keep looking at the clock. Time will go slower
Teach yourself some little tricks; flipping a coin or ring in your fingers, teaching yourself to cry on the spot or even try to wiggle your ears, bend your tongue into a tube/roll or try not to blink for a long time.
Count in your head and see what number you can get to. Don't go ridiculously fast but don't lose momentum either.
Take a crossword puzzle with you.
Print off 100 riddles on paper and try and make them last the whole day. Spend time to work out each one.
Count things. Set yourself a target; how many red things can I see today?
This all depends what type of job you do. If you're on a shop floor, some of these would be okay as long as you're not ignoring customers
