Yes - they are USB plug and play. Scanners are very simple devices and can be bought from �20 upwards.
Most people prefer an all in one printer, scanner, copier. Mine is 5 years old and has been no problems at all. You can buy one from around �40, but I would prefer to pay more.
If you already have a good printer then get a scanner. This one looks good - and doesn't need a power lead:
http://www.amazon.co.uk/Canon-Lide-Colour-Flat bed-Scanner/dp/B0009Y6AZ6/ref=pd_bbs_sr_2/026- 9373653-3371612?ie=UTF8&s=electronics&qid=1185 559510&sr=8-2
Decide what you want and shop around for the best deal.