I use Kodak Wratten filters and have found them a godsend at that last minute in a pinch, especially when using DLP projectors which start from a full white light and therefore need more blocking.
I often use cheaper R-72 filters though on other projects (or with LCD projectors) because that allows more light through and works fine (always accept "good enough"). It depends on what you're working with. But I always keep that Wratten in my bag, just in case.
Since I'm in Europe, I use this place, because it's got all sorts of crazy lighting filters and devices that, if you're adventerous enough, you can do some amazing things with:
Apparently they have a US outlet. There are other distributors/competitors selling similar instruments, but I've found Edmund Optics pretty good for all around filters I need, with accurate charts. I also buy Micro lenses from them, because they allow me to work in tight corners with cheap cameras (anything from garage sale Logitechs up to Unbrains) and not have to worry about removing the IR-Cut filters.
When you use Visible-Cut filters, you also have to think about infra-red lighting. I have yet to find the ideal lighting solution on this front, although there is a new product that looks appealing (although somewhat expensive):