What external IR receivers are there for Mac?
If you're looking to control Keynote presentations and your Mac doesn't have a built-in IR port, you could buy an external receiver, but I suggest you use either:


The Keynote Remote app for iPhone. This works over wi-fi and requires only a $0.99 purchase and no additional hardware to buy or set up.




or


A specialized slide advancer, like this Logitech one. This is designed to be comfortable to hold (the Apple Remote wasn't) and doesn't require line-of-sight to the receiver (which is a small USB dongle) to work. Some of the better ones have a slide counter and laser pointers built in.