Grab a copy of SpyWare Blaster. It install a regularly updated set of kill bits for both IE and Firefox and installs a list of sites to block (known adware/badware purveyors). Free from JavaCool:

http://www.javacoolsoftware.com/

They also make a cool tool called EULAlyizer which parses most EULAs and highlights passages you should probably understand before clicking "OK".