Everyone keeps weight in different places.. Yours is the belly.. Crunches will help your core strength but will do very little to get rid of the belly fat.. This site has some great exercises, scroll down to the core section:
http://www.frixo.com/sites/fitness/exercises.html
Personally for me I need to do weight bearing exercises like running or racquetball to cut down the midsection.. RB seems to help the most..