Thanks to Boing Boing for pointing me to the article, “Ten most needed circuits for the DIYer” on DIYLive. The ten circuits include an audio amplifiers, RC lowpass filter, and power supply.

DIYLive looks like a very cool website for ham radio types. A quick scan turned up other articles that hams will find amusing and useful, including:

1. Cheap LEDS and
2. Circuit Symbols for Noobs