The best option (which is the one I used) is to buy a used Minolta/Canon/Epson/Nikon dedicated film scanner off ebay, use it to scan your slides, and then sell it again. For me this worked out to cost me $100 (Aus). I did this 3 years ago, and I had about 35 rolls of negative film to scan.
You get better quality with a dedicated film scanner, and you also get the benifit of what ever cleaning mode they have to make sure you get a clear scan even with scratched negs and slides.
One thing to remember is that you will be spending about two hours per roll of 36 if you want to do it properly with two pass scanning (at least this is how long it took me).