You'll get the best results and have the easiest time with a scanner specifically designed for handling 35mm slides and negatives. It would be hard to go wrong with the Nikon Coolscan V ED, available for around $500. The machine will scan your pictures quickly and with a minimum of fuss.
One advantage of the best slide scanners, like the Coolscan, is that they come equipped with software called Digital ICE for automatic fixing of scratches, dustiness, and other defects.
You can spend a great deal less and still get satisfactory results, although the machines won't work as quickly or simply. Scanners from Canon, Hewlett-Packard, Epson, and others come with slide attachments or offer them as accessories. The Epson Perfection 4180 Photo, which includes a slide adapter in its $200 price, makes a good choice.