K9 Web Protection is a web filtering and blocking software that is extremely configurable. You could turn on/off all the settings that you did/not want;filtering, word block, site block, category block,Internet time feature, content-based browsing, and more... You can set what hours of the day you want the Internet on the computer to be blocked, and can customize each day of the week. All settings are accessed via the web browser, and are protected by a password, which you could give to someone else and not know yourself if you wanted to completely block access. It works cross-browsers; one configuration covers Internet Explorer, Firefox, Chrome and others all one the same machine.
Have used myself, with great results...highly recommend!
K9 Web Protection: http://www1.k9webprotection.com/
Did I mention that it is free?