OpenDNS is handy. You

1/ Sign up for an account 2/ Configure your home's router to use their DNS servers 3/ Install an agent on a machine in your home's network, authenticate it with your account credentials. When your router's IP address changes, this agent makes sure to update your account. 4/ Configure the sites or types of site you want to block.

Once you're up and running, If a DNS request from your network matches something that'd be blocked, you'll get re-directed to a "Blocked Content" page.