Mac: There are a lot of tools that will convert videos for your iPhone, iPod or iPad (like our favourite, Handbrake), but they aren't always easy for the average person to use. iConvert makes it as simple as drag, drop and click.
iConvert will not only convert tons of video formats to an iOS-friendly movie file, you can also send them straight to iTunes when the conversion is done. Just drag the file into the window, choose your device from the dropdown list and click Convert. It isn't actually that much faster than something like Handbrake, but for the less tech-savvy people in your life, it's going to be a lot less intimidating and confusing -- and you'll be off the hook for helping them convert videos.
iConvert is a free download for Mac OS X, though the $7.49 iConvert HD has a number of other features, like the ability to encode multiple videos at once, encode videos in HD, and choose from "higher quality" or "smaller file size" on a simple slider (though it does have a slightly more intimidating interface).