Ever wondered how your Christmas lights stay lit when a bulb goes out, even though they’re all wired in series? EDN has the answers in a nicely technical article here.

Most of you have probably thought about building (or have already done so) a system to automatically water your Christmas tree. Mark McCuller designed a nice system that uses water level sensors to maintain a precise water level at all times. Click here for the extremely detailed plans in PDF format.

Lastly, click here for some good instructions on how to build an electronic circuit that sequentially cycles power strings of Christmas lights (turning on and off entire strings at one time, not bulb-by–bulb control).