I have a few covers to go over my cloth nappies, for the flats I find the Thirsties Duo Wrap covers to be best. I had 2 size ones, and am currently using 4 size twos. 3 with velcro, and 1 with snaps. My 5-month-old is currently in the size 2s with all the snaps done up. The size 2s are supposed to go all the way to 3 years so I will see.
I also have some Gen Y Covers in various sizes as they do not have the snaps down the front to change the fit dramatically, and some homemade plastic pants type ones.