We use alix and Soekris boards for all kind of nuts and bolts networking and automation around here. The alix is from switzerland and hard to get hold of but if you're in the usa and want to get into this, the soekris is easy to get and use. They are full X86 computers that can run standard distros off compact flash and only require about 5 watts.
Get them right from the source in California at www.soekris.com. Soren and crew are great guys as well.