Enter a chemical name, draw a chemical structure (substructure, similar, or exact match), or upload a structure, and Chemicalize.org will search the Web for pages that have been chemicalized. The result contains structures and the Web pages that include the target structure. It is also possible to find properties. Check out this video for a quick demo.
TechXtra is a search engine for computing, mathematics, and engineering. It searches 25 different collections for articles, books, Web sites, industry news, job announcements, technical reports, technical data, full text eprints, the latest research, and teaching and learning resources. TechXtra includes content from over 50 publishers and providers. There are basic and advanced search modes.
Wolfram|Alpha is an excellent resource for finding chemical information such as unit conversions, flash points, thermodynamic properties, reactivity, and boiling points. It also provides rapid and accurate computations. Examples of chemical information found in Wolfram|Alpha are available here.