yes you can. It's been a long time but there is a cable (small ribbon cable) that will allow you to do it. You'll only use one of the cards for vid output, and at the time it was a real screamer. I don't remember the exacts anymore, but you may want to do some searches for linking VooDoo cards.
For the preformance and price tho, it's better and cheaper to upgrade to the 5500 which would smoke the "dual" setup. You could sell your cards on ebay for about $35 each and the 5500 is less than $100 now so you'd pay little for a much better card.