I was surprised pleasantly that my several-years-old SCSI-based Epson 1200S scanner handles slides. Yes, I bought the optional extra slide scanner, which projects a soft white light down through the slides into the body of the scanner. It is large enough to handle four slides at once.
The TWAIN software that controls the scanner lets me specify negatives or positive slides. It is smart enough to find each of the four slides, and scan them to individual image files. (Once in a while, it gets fooled, and scans the slide incorrectly. Also, it can't know which side of the slide is the front!) When scanning fim negatives, it corrects their color.
The resulting image size is roughly 1800x1128 -- actually 300dpi or about 2 megapixels. You can save it in whatever format you prefer; I use JPEG with a low-level of compression.
My dad pays my kids 15 cents/slide to digitize his old slides from the 1950s and 1960s. After scanning four at a time, they run the images through PaintShop Pro 8's Enhance Photo script, which fixes faded and shifted colors. (Slides often tend towards pink or blue over the decades.)
The photo above is the scan of a slide taken 40 years ago at the Checkpoint Charlie, the (in)famous crossing point between the American and Russian sectors of Berlin. (Click the image to see the photo, reduced to 800x500).
The Enhance Photo script does a great job, most of the time. Some photos it cannot fix, and others are better left unenhanced. It also doesn't deal with dirt, scratches, tears, and mildew. The photo at right shows a closeup of the sky portion of the Checkpoint Charlie photo: you can see dirt/mildew.
My friend Don Beaton has a Nikon slide scanner. These are a lot more expensive and the software has a lousey user interface, but they do a much better job by removing speckles.