Jon Scott's Site - A great web site from another home automation enthusiast.
Smart Home - Good site for home automation gear, especially X-10 modules. They have their own line of high-quality X-10 modules. Not always the best price. For many things, shop around on the web first.
Xantech - A manufacturer of some very good home automation equipment. I especially recommend their IR components.
Custom Solutions, Inc. - Makers of the awesome Home Vision Pro home automation controller.
Channel Vison - Manufacturer of home automation audio and video gear. I have had good experiences with their video modulators.
Worthington Distribution - An excellent home automation e-tailer with great prices.
Hometech Solutions - Yet another home automation e-tailer I have used. This is where I bought my Xantech amp. The initial shipment was the wrong amp, but I received excellent service getting it resolved. I have ordered other things without problems. This site also has some how-to pages.
Applied Digital - They have a less expensive home automation controller called the Ocelot. I have not used it, but a lot of people recommend it.
RCS - Manufacturer of X-10 and serial controlled thermostats as well as other things.
James Lipsit's Site - Another excellent site about a guy's home automation system. James uses speech recognition in his system.
Girder - A powerful bridging software used to control windows applications. I use it to control media player and for text-to-speech via its serial plug-in.
HouseBot - PC-based home control software now owned by Meedio. Not free any more, but still less expensive than many and has a very good design. I plan on using it for control of my touch panels.