There is a world of useful search engines outside Google. All use slightly different methods and can return different selections of results. Here are some starting points.
A9 is an interesting alternative to Google for finding a variety of materials, such as links and images, simultaneously.
Google themselves have a useful search engine for academic material at Google Scholar and one for books - both titles and text - at Google Books. Out of copyright (full text) books can be found by restricting searches to those published earlier than 1923. If you are after on-line books try The Online Books Page
Papers and other articles, both academic and general interest, can be found at Findarticles, an offshoot of LookSmart
A specialist search engine for science topics is Scirus
An entirely different approach to searching is to see what has caught the interest of a community. There are several 'social bookmark' sites, try Del.icio.us and Ma.gnolia, for general users. CiteULike uses a similar method to capture informal citations for the science community.
My prediction is that sites catering for very specific communities, like CiteULike, are soon going to become the most effective way to keep informed and track useful information.
Please see our Resources pages for more suggestions, or drop me a line if you have any interesting links you think should be included.