In addition to varying in levels of absorbency, diaper covers run the gamut in style, from basic to fancy: Some are pull-ups, while others fasten with snaps or Velcro or Aplix tabs, and they come in lots of colors and patterns.
When the weather is warm enough, many parents let their babies bum around in diaper covers; this also makes for quicker changing. You'll probably want to have five or six. They can be reused two or three times before they need to be thoroughly cleaned; just wipe the inside with a damp cloth. Prices start at about $8 and top out at $18 or so.