The Right Site ® has hundreds of thousands of free demographic profiles, based on Census of Population and Housing data. EASI Census 2010 Quick Reports are available for area codes and TV markets, as well as the usual geographic divisions. (Registration is required.)
A ZIP code lookup site with neighborhood lifestyle segmentation information is MyBestSegments, offered by Nielsen, with its PRIZM Segmentation System.
You can register with the firm ESRI for access to demographic and lifestyle data with a free trial of their Business Analyst Online, and you can read the descriptions of their Tapestry segments.