I read that if the concrete is flat, you can put pavers over it, even the rubber mat kind designed for outdoor patios at Home Depot. There is another kind that looks like deck wood that comes in squares that you just snap together.

We put recycled rubber tire tiles over ours, got them at Home Depot and they're fabulous. And really, really heavy! They clean up well and covered our cracked concrete patio perfectly: http://www.homedepot.com/webapp/catalog/servlet/Search?storeId=10051&langId=-1&catalogId=10053&keyword=rubber+tiles&Ns=None&Ntpr=1&Ntpc=1&selectedCatgry=Search+All

If the slab is in acceptable condition, drains away from the house and is low enough below any patio doors to allow finish clearance, it can be an excellent base for new finishes. A popular finish that we install are slate tiles. Also pavers, brick and wood decking. You can usually set the tile on a thinset morter on the old slab, and decks can sit on sleepers or use the snap together deck tiles as mentioned above.