The ANSI Webstore will let you search for standards from ANSI, ISO, IEC, ASTM and other standards publishers by keyword or document number. Keyword searches may give results from multiple sources including standards that are feely available on the Web. The left side of the page provides the ability to browse by publisher or view all standards developing organizations in the database.
IHS is one of several companies that sells copies of industry standards. The site provides an excellent search engine to standards of all kinds and will often mention whether a particular standard has been superseded or revised more recently. Searching by title keywords will help locate information on whether a standard has also been issued by another standards agency.