A "voltage regulator" is designed to hold a constant output voltage.
A "switching voltage regulator", usually called a switching regulator, also called a DC to DC converter, accomplishes this goal by rapidly switching a transistor from full on and full off.
A "linear voltage regulator", usually called a "linear regulator", accomplishes the same goal by holding a transistor in its active region, somewhere between full on or full off.
The 723 Voltage Regulator can be used as either a linear or a switching regulator.
The Linuxstamp uses a the LTC3407-3 switching regulator.
The ARMUS Embedded Linux Board uses ...
The MCP1252/3 Flyback Switching Regulators can generate an output voltage greater than the input voltage -- something impossible with linear voltage regulators.
- The 3-transistor Black regulator: cheap, high-efficiency, current limited.
- http://smps.us/ "SMPS SWITCHING POWER SUPPLY DESIGN CIRCUITS, SCHEMATICS, PCBs, ELECTRICAL ENGINEERING REFERENCE, SOFTWARE, AND OTHER FREE ONLINE RESOURCES" ... including http://smps.us/layout.html "PRINTED CIRCUIT BOARD LAYOUT GUIDELINES FOR SWITCHING POWER SUPPLIES (SMPS)"
- Massmind: Power discusses a variety of linear and switching power supply regulators
- "boost converter hack" describes one way a microcontroller (uC) can control its own supply voltage, once it's given an initial push. (External diodes would be better than re-using the internal diodes, to avoid exceeding the manufacturer's recommendations).
- "AC DC Switch Mode Supply Controller Via PSoC" discusses programmable current source switching mode controllers.