Here we have my colour classic running a modern USB Apple keyboard mouse. How you say? Well, a chap called Steve at his site http://www.bigmessowires.com/ makes several unique and quite clever gadgets for vintage mac owners. There is more info on the ADB <> USB converter here: http://www.bigmessowires.com/retro-usb/ but essentially its a hardware converter for either using a USB keyboard and mouse with an ADB equipped mac or using an ADB keyboard and mouse with a USB equipped device. Hardware aside, the board currently supports ANSI and ISO mappings. US keyboards are fully supported while others are via the ISO standard. It’s firmware is upgradeable via USB flash.
If you have a vintage mac please check out the links.