OctoPrint provides a snappy web interface for controlling consumer 3D printers. It is Free Software and released under the GNU Affero General Public License V3.
It is a cross between a baby monitor and remote control for 3D printers
OctoPrint monitors the status of the print job and the printer itself, including the temperature of the print head (hot end) and the temperature of the bed if the bed on the printer is heated. OctoPrint can also show the output of a connected webcam to monitor the state of the print and visualize the G-code in sync with the print job or asynchronously.
OctoPrint has a plugin system, allowing users to extend functionality. There are currently over 150 open-sourced plugins listed in the official plugin repository.
Watch Gina (creator of OctoPrint) walk through examples of using OctoPrint for consumer 3D printers.