X3watch is a good free alternative to Covenant Eyes, although Covenant Eyes will give you a much more detailed report of internet activity. X3watch only lists questionable sites, where Covenant Eyes will rate all internet activity on a detailed scale for the accountability partner to see. Try both. Feel free to click on the Covenant Eyes link on the bottom of this page to try a free 30-day trial.
As far as further protection beyond accountability, there are filters available from both Covenant Eyes and XXX Church (SafeEyes software). I would recommend at least the accountability software, and a filter if you think that is necessary. Filters alone are not sufficient protection, in my opinion...too easy to get around.