if your using squid auth its a pain to have to plug in usernames and passwords in multiple applications, especially if your want automation for updates etc.

The following shows sample rules to allow access without a password to certain sites. 

Spybot Updates

acl spybot urlpath_regex  spybotsd.ini$ includes.zip$ english.zip$ advcheck.zip$ tools.zip$  clsid.zip$ skins.main.zip$

http_access allow spybot