(Posted in 2 parts):
You need a film scanner to scan your negatives. If your negatives are on 35mm film then many flatbed document scanners have a 35mm film scanning facility built-in. You'll need to consider what type of quality you're hoping to achieve and how much you're prepared to pay. Cheaper scanners may only scan at a resolution of 600dpi and (even though they might claim to scan film) this just isn't good enough for anything other than very grainy results. For an indication of the type of scanner you might need, see the Canon models, here:
http://www.canon.co.uk/for_home/product_finder/scanners/ flatbed_with_film_scanning/index.asp
The basic model, 3200F, has a resolution of 1200 x 2400 dpi and this will be just about adequate for most people's needs. The next model up, however, (4200F) has a much better resolution of 3200 x 6400 and doesn't cost much more - they're both sub-�100 - so this is the one which I'd recommend. (Yes, I've got one and no, I don't work for Canon!)
As you go further up the range, resolutions don't significantly improve but you get added features like the ability, on the 8400F, to scan up to 12 negatives at once. (The 4200F only takes 4 at a time). However, the prices of these high-end scanners are much higher than the basic two models.