I built a simple tube transmitter a while back that gives me about five watts out, and it's fun to sit down with this transmitter and, say, one of my portable SONY receivers and make QRP contacts. An hour or so ago I worked a guy up in Maine, who was also QRP with 3 watts. It's very "old school" and minimalist. Very cool. I've also build the little Rockmite transceiver and am currently working on one of the Ten Tec kits (a transceiver for 40 meters).