Google labs is a beta testing area of Google's features in development. When going to http://labs.google.com/ users can try such features as:
Google Glossary - a lexicon. Look up - definitions, phrases and acronyms
Google Sets - Automated online creation of sets from several items
Voice Search - Search the Google database by phone. Go to http://labs.google.com/gvs.html first, and then dial this number: (650) 318-0165
Keyboard shortcuts - Navigate your seach results using your keyboard (MSIE 5+, Netscape 6+, Mozilla, JavaScript and Cookies required)
Google highly encourages users to try and experiment with the prototyped features, but does not guarantee that all of them will make past the development phase. The features above are as of June 5th, 2002.
Update December 2002, two new features are available:
Google WebQuotes - a sort of recomendation engine, a serious version of googlism
Google Viewer - a tool for automatic viewing of search results, still needs some work, IMO.