Google has introduced a prior art search tool to search journal articles, books, and trade publications in addition to patents. Once you've done a search and opened a result page, look for the blue "Find prior art" box at the top.
Google is also now searching patents from the European Patent Office. For more information about the international patent search and the prior art search tool, see the Google blog entry, Improving Google Patents with European Patent Office patents and the Prior Art Finder.
For a more definitive classification search of international patents, Fondren Library is now offering a one-hour introductory class about how to search for international patents online using the European Patent Office Espacenet interface directly. For class times call 713-348-5483 or access the patent searching class schedule.
A tutorial for using PubWest to search for both U.S. and international patents is also loaded on a library computer used for accessing PubWest.