Bac-out could help, too. I just bought a bottle of it today, so I don't have personal experience with it, but I've heard lots of good things about it. It's an enzyme cleaner, so you squirt a little on poopy dipes and voila, no stains on washday. Right?
and I've had good results with it. I did put it in a squirt bottle, though, because I found that the bottle didn't last long if I was just using the pour spout. I keep the spray bottle by my changing station and just give them a good squirt before dropping them in and then I keep a bottle in the laundry room and give an extra spritz to anything that doesn't come out in the prewash (which is rare).