The Dimension Engineering 5V switching regulator is a tight & tidy voltage regulator that offers great performance at an excellent price. Great for extending battery life!
Why would you need a DE-SW0xx series switch mode voltage regulator? Easy. Power efficiency. A regular 78M0x series linear regulator wastes the power that isn't being put to good use as heat. A switch mode regulator uses a different approach from just "throwing the power away", which means batteries run longer and the regulator runs cooler. These units run up to 87% efficient!
These modules are designed to be pin-for-pin compatible with a standard 78M0x style regulator, so you can plug it into any circuit calling for a wasteful linear regulator.
These devices are small too! The body is only 16x22mm, and only 11mm deep, and come pre-pinned with convenient breadboard-compatible 0.1" spacing.