I would like to list here a few webpages, which I strongly recommend to visit.
There are already QRP clubs almost in each country: the "crazy people", who transmit with 5 or 10 W around the world. And they also still united in clubs. Unbelievable!
If you have already envisaged to build a transceiver by yourself, those QRP rigs will surely be interesting for you. Get to know everything at the DL-QRP-AG (German Working Group for QRP and Self-Construction, in German) and the QRP-Forum about availability of kits, tips and tricks for example in the FAQ.