It seems like every stake or general conference has some talk(s) about pornography. Those messages are being stressed at the ward level, too. In fact, our bishop often says "There's a King David in everyone." Our stake presidency asks, after every temple recommend interview, whether the interviewee has a filter on their home internet service.
To that end, I thought I'd share the ones we use here at home. Lance recommended to us "Naomi" and we installed that. The only knock on it is there is little control over what it does or doesn't block. For example, I could never read an article on ESPN because it would assume something was inappropriate and immediately close the browser, when in fact there was nothing worthy of censure. We had the same problem trying to access MSNBC before they changed the layout of their home page. Weird.
Our stake presidency and bishop recommend "K9 Web Protection." This one gives more control and allows the administrator to block or allow certain sites (like ESPN!). K9 also keeps a detailed web history so the administrator can check any sites visited by anyone on the computer.
Both filters are free and we actually have both installed on our computer. While most of us probably don't have any problems with pornography (It's never one of us, right?), it doesn't hurt to keep the temptation as far away as possible!