Alex at Tinkerlog writes:

For my latest projects I used a lot of single cell LiPo batteries. They are really nice. High power density, low self-discharge, no memory effect and they can deliver quite an amount of current. But LiPo battery handling is a bit more complicated than other rechargeable batteries. You have to take care of under voltage and over charging as that may destroy the battery.

I used the Sparkfun LiPoly charger, based on MAX1555, for some time and it works really well. The only thing I missed was a way to control the current. After some research I decided to try another chip, the Microchip MCP73833.

LiPoly charging with MCP73833