I don't actually have one of these, but ever since Dan Goldenberg raved about this on his year-end "tried and liked in 2005" posting over on the iBOB mailing list, I've wanted one. The Kelly Kettle is a modern, yet very traditional, recreation of the Irish fisherman's kettle. Their website explains how the kettle works. Essentially it's a double-walled flask that holds water. You build a tiny fire in the base and in about five or six minutes you've got boiling water for tea, cocoa, instant coffee or whatever.
For most of my fast and light bike trips, I've been going without cooking gear. But there is something very nice about firing up a quick hot beverage first thing in the morning or at a quick back-country lunch stop. The little one-pint version of the kettle weighs a bit over a pound, and that weight might be worth carrying around. It's definitely lighter than packing a separate stove, fuel and cooking pot.