Standalone power for arduino uno with batteries

I bought a few of those 9V connectors for the uno and used a standard 9V battery. The thing is that it dies within a day or two. Not useful for long term project. Does anyone have any suggestions or a tutorial on how to use batteries to power the micro-controller and any sensors without having to change batteries every two days.

If you mean the PP3 style of 9v battery then they are next to useless for an Arduino. Try a pack of 6xAA cells.

You may also be interesteds in Nick Gammons low power tutorial

...R

Try a 3AA/3C/3D battery pack and power the Uno via 5V pin on the power header, or via the USB connector.
Then you're not giving up 44% of your battery life as heat in the 5V regulator.
You can also use a switching regulator to make 5V from a lower voltage or from a higher voltage more efficiently than a linear regulator as well, see the regulators at www.pololu.com for examples.