Reddit mentions of Rode Microphones MiCon-3 Adaptor for HS1 Headset, Lavalier Microphones

The Rode video mic is great, but if you're only going to do interviews, consider getting the Rode lavalier mic. I own them both, and while a shotgun (the video mic) is great for getting directional sound, the lavalier is specifically intended for capturing somewhat localized sound, like one person talking. The Rode lavalier is actually omnidirectional, so you just might be able to capture decent sound from several people, depending on the environment.

Should you chose the Rode lavalier, don't forget to buy the appropriate "Micon" adaptor (probably either the XLR-version or the standard minijack).

You could plug the lavalier directly in to your 60D, or even better into some typer of recorder, like the Zoom H4n or H1, for better quality sound and more control over levels and such. The H4n gives you the added option of recording additional ambient sound (four channel recorder) as a backup, just in case the mic fails, while the H1 (two channels) is very simple and straight forward. If possible, run a minijack-cable from the recorder to your camera, so you can easily sync sound to video in post (also, you'll get a backup recording of the sound in-camera, perhaps even good enough to use without syncing).

I'm guessing there's a ton of cheap alternatives, but the Rode and Zoom combinations have worked well for me.