.htaccess / .htpasswd bypass if at a certain IP address

For versions 2.2.X you can use the following…

AuthUserFile /var/www/mysite/.htpasswd
AuthName "Please Log In"
AuthType Basic
require valid-user
Order allow,deny
Allow from xxx.xxx.xxx.xxx
satisfy any

Obviously replace the path to your usersfile and the ip address which you would like to bypass the authentication.

Further explanation of the specifics, can be found at: http://httpd.apache.org/docs/2.2/howto/auth.html