Are you doing a lot of home automation projects? Are you finding it complicated to do with larger systems like heaters or air conditioners? Instructables user rjkorn makes it simpler with this solid state relay project that you can make with an Arduino or Arduino-compatible board.
The author of this post uses things left over around the house from other projects, for the most part. They also use a chipKIT Pi as the brain of the operation.

The module is framed around a scrap box with a couple of relays. Then, heat sinks are added for convenience and safety. Wire is then run to ground, and you can connect the system you want to automate!
What home automation projects are you working on? Do you think this would prove helpful for you in simplifying and testing? Let us know in the comments below.