This circuit can output 5V.The circuit can charge things like Ipods, PDAs, other devices that plugs into a USB to charge.The circuit very simple.All the parts can be easily purchased at your local electronic store, like Radio Shack.source

This is a charger for lithium ion batteries which takes its power from the USB port of a computer.It uses the MCP73861 or MCP73863 Li-ion battery charger chip manufactured by Microchip.The circuit is very simple to build based on the application note.source

The charger in this project is designed to charge two AA NiMH or NiCd cells of any capacity (as long as they are the same) at about 470mA. It will charge 700mAh NiCds in about 1.5 hours, 1500mAh NiMHs in about 3.5 hours, and 2500mAh NiMHs in about 5.5 hours. The charger incorporates an automatic charge cut-off circuit based on cell temperature, and the cells can be left in the charger indefinitely after cut-off. source

USB power bus is a great source for charging a single-cell Lithium-Ion battery. This circuit shown you how to build a USB-powered single-cell Li-Ion battery charger using National Semiconductor s LM3622 Li-Ion Battery Charger Controller.The battery-charger circuit is designed to operate as a high power USB function. To be compliant with USB Specifications (Rev. 1.1), a high-power function must not draw more than 500 mA from the bus during normal operation. The LM3622 uses the 0.25 current-limit resistor R1 to set a 400 mA maximum charging current. This leaves a 100 mA surplus that can be used to supply USB control circuitry and other functions in the device.source

A USB port is a great power source for charging a single cell li-on battery. It is capable of supplying maximum 5.25V and 500 mA. This circuit is a USB powered single cell li-on battery charger. LM3622 is used as the controller. This special purpose IC has a precise end-of-charge control and low battery leakage current about 200nA.source