Is there a good place to go to identify what kind of slot my spare video card uses?
A site that shows pictures of the various slot types so I can identify this one?
See if you can find your graphics card slot/connector in this hardware identification chart:
Specifically, check the rightmost column, in the sections titled "Peripheral Cards" and "Desktop Card Slots."
Your spare video card probably uses a PCI-Express x16, AGP, or PCI slot. (listed in order from fastest/newest to slowest/oldest)
There are a few (very few) motherboards with integrated video that also support special pass-through riser cards. If that's the case, your best to identify the slot bet is to find a model number on the card or motherboard, and search on Google or eBay. But if you just need a card, you can get a card that will fit in any of your other expansion slots.
PCI-e card (x16)
PCI-e slot (x16)
and just for the craic, here's an ISA graphics card :)