Are you tired of being distracted by the internet? Twitter, Flickr, YouTube, and Google Earth could all be considered "distractions" or "time wasters." So, if you're looking to get some work done without physically un-pluging from the internet then Freedom might be what you need.
Freedom allows you to set a time limit for internet access. For instance, if I need to set aside 30 minutes for a project that doesn't require internet access, I could tell Freedom to block internet access for those 30 minutes, Freedom will then disable WiFi and ethernet access for 30 minutes. After the 30 minutes are over your WiFi and ethernet access will be restored.
You can download Freedom for free (donations accepted) from the developers website or from MacUpdate.