Once every year I get to remind my boss how "old" he is (old in quotation marks because he's only 4 years older than I am, and neither of us are actually old) I like to do this by decorating his cubicle for his birthday.
This year I spent a total of $5 at the dollar store, and produced fairly good results - and that included a card!
I decided against the Disney Princess theme and went with something slightly less emasculating and less obnoxious - hockey theme!
I also picked up some streamers, balloons and tissue paper! Streamers and balloons are pretty obvious as to what to do with them, but the tissue paper I took one sheet at a time and grabbed it by the middle and stuck it in random crevices...like between his monitors.
So for not very much money, I was able to decorate the cubicle and still have plenty left over!