Before a workout, if I haven't had a meal in the last 3 hours, I'll have something light, like maybe a ripe banana.
After a workout, it's important to get and easily-digested source of some good carbs and a bit of protein (about a 4-to-1, carbs-to-protein ratio) to replenish glycogen stores and start anabolism rather than catabolism. I have a smoothie (often a "Vega" meal replacement with some frozen fruit added, or a Nutiva smoothie mix with some Vega added in.)