working the chest

the chest is composed of the following muscles:
*pectoralis major, sternal
*pectoralis major, clavicular
*pectoralis minor
*serratus anterior

e.g. if you're "stuck" on bench and cant safely go up in weight, try doing exercises that work all of these areas, e.g. lever pec deck fly:
http://www.exrx.net/WeightExercises/PectoralSternal/LVPecDeckFly.html

here's a good place to start for choosing chest exercises:
http://www.exrx.net/Lists/ExList/ChestWt.html