As I point out in my book, Genealogy Online 8th Edition, you can do a lot of good research using search engines and Boolean operators (AND, NOT, OR, and parentheses.) Recently, Yahoo! has stopped supporting the operators NOT and AND, although the plus or minus sign in front of a term still work.
The NOT is very important to genealogists searching for surnames that are also common words: BROWN, FOX, BANKS, & WEEKS are just some examples. To find genealogy pages for these surnames in Yahoo now, be sure to put a minus-sign directly in front of a term that you want excluded from search result (meaning that Yahoo! will exclude pages that has that term in their text) and a plus sign in front of terms you must have. So to get hits for pages with genealogy and Banks surname, instead of
BANKS AND GENEALOGY NOT FINANCE NOT RIVER
you would formulate it as
+BANKS +GENEALOGY -FINANCE -RIVER
The OR operator still works, and the AND is assumed if you use no operators, but nesting with parentheses doesn’t as in
+(BANKS AND GENEALOGY) - (FINANCE OR RIVER)
Advanced Google still accepts the most popular Boolean terms, and Exalead even supports the NEAR operator, which really helps with common surnames, but Live Search is now the only major search engine with full Boolean support.
For more details on how to do the Boolean Boogie for genealogy, read Genealogy Online 8th Edition.