The American Society of Home Inspectors is a certifying organization of home inspectors in the United States and Canada. At the organization's site you can learn about what you should be on the lookout for, such as building defects, safety issues, security aspects, and environmental concerns. To begin you can find out exactly what a professional home inspection entails and the reasons for getting one done. Also laid out before you are the ASHI Standards of Practice and Code of Ethics that certified inspectors must adhere to. There are articles about lead in drinking water, the dangers of aluminum wiring, and septic tank information.
Several links take buyers and sellers to other sites with information on construction defects.
The ASHI site has recently undergone an overhaul, so hopefully it will expand in the coming months.