Many of us love building our own electronics. Many circuits require a regulated 3.3 or 5 volt power supply though. snapVCC is a handy solution that lets you use a 9V battery to power your electronics. It snaps right on your 9V battery and uses a buck converter for a more efficient performance.
snapVCC lets you switch between 3.3V and 5V output by switching a jumper. snapVCC also has an LED power indicator and reverse polarity protection. It is an open source hardware project.