I own a Creative Labs Voodoo2 SLI (2 x 12Mb's).  Is it possible to link up more than just 2 cards? Would it be possible to maybe link up 4, or 8 even (if a motherboard has 8 PCI slot's :o ) ??

Would it be possible??

nop. as you may noticed, the cards have just one sli-connector which is fully used when you connect 2 boards. the chips thereselfs are able to and that's what quantum3d made use of with their amazing obsidian boards series..i don't think that there's another firm who made a larger varation of the voodoo2 sli system

Micha's correct!

Quantum3D made cards with two Voodoo2s SLIed on one card.  And then they linked them together!  So this rig is eight Voodoo2s!

http://www.procerus.btinternet.co.uk/Mercury.jpg

But the advantage was that it enabled anti-aliasing in hardware at a time before other graphics cards came with the capability.  The Quantum3D Heavy Metal Mercury could only run resolutions up to 1024x1024 and only had drivers for Windows NT.  But it was used for technical demonstrations of the upcoming Voodoo5's capabilities before there was usable silicon.

I hope to own one in time...  ;)