Some posters have mentioned Vistaprint before as a source of cheap business cards.
Word of advice -
DON'T!!!
What these scammers do is when you order cards, they sign you up for all sorts of companies, like "Vistaprint Rewards" which then take £10 or so off your credit card every month.
It *may* be possible to avoid this by ticking virtually invisible check boxes when you order your cards, or by cancelling membership of these scheme, although I've spent the last half-hour trying to do so with no joy.
These companies are all off-shore, in places like Bermuda etc, so are not easy to deal with, and probably outside the jurisdiction of UK laws.
So I've just cancelled my credit card as the only safe option.
For a LOOOOOOONG list of bad customer experiences:
http://www.consumeraffairs.com/online/vistaprint.html