they do make video cards with multiple DACs (up to 4 I think) but they are designed for CAD and not your average home user or gamer. I think 3dlabs makes/made them.
But no, there is no way to take a single Nvidia GFFX or GF4 AGP card and allow it to handle more than two monitors by itself. HOWEVER it may be possible for the NVIEW software to handle more than two if you installed another Nvidia card. For example, a GFFX AGP card and a GFFX 5200 PCI card in the same machine. Or maybe even a GFFX AGP + GF4MX PCI card. I say this because they use the same detonator driver package anyway.
But even if NVIEW doesn't understand, hope is not lost. My friend uses 3 monitors with a Radeon VE AGP + Rage128 PCI combination and it works great, and that's handled by Windows not the driver package. Radeon and Rage128 use completely different driver packages yet Windows itself will allow you to use one big Desktop setup for multiple monitors and cards