You can also get USB to DVI adapters. They cost ~75$ each they are no good for gaming but for general use they work great just plug in and go. They are also portable and make running 3+ monitors off a laptop possible. You can use up to 8 of them they say (never tried myself) I run two monitors off a card and two more off the Uvplus adapters.
http://www.evga.com/uvplus/
http://www.evga.com/uvplus/
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