One would assume that Academic institutions provide their learning technology departments with the finest machines from which to develop on. However, for those not so fortunate, here is a fantastic article on speeding up that sometimes machine chugging Photoshop:
How to make photoshop faster on slower computers
Also as a bonus for those who don't have photoshop, or just can't get it running fast enough for simple tasks. picnik is a fantastic web based app for photo editing.