Online card sorting tools are fascinating because you can send a link out to  200 participants and simply look at results, or you can use a screen-sharing program to conduct card-sorting sessions 1-on-1 with participants. And for the win, you can go crazy and do BOTH. Either way, you’ll need a tool, and these are the ones we’re aware of:

Web Sort – the first online card sorting tool and still going strong.

OptimalSort – from the guys at OptimalWorkshop who make a few remote UX tools.