This page has a bunch of circuits I've found to be useful or have built
or will be building in the near future.
Most are related to home automation, astronomy, etc.
Circuit Cellar Magazine * Home Power Magazine * http://www.electronic-circuits-diagrams.com/
Circuit 001: a temperature based pulse modulated fan controllor
555buzzer
alarm circuit using small wire
fluidlevel indicator
Rain Alarm
4in1 Alarm
Dew detector