The Charge-o-matic is a miniature USB powered single cell Lithium Polymer Battery charger.

Simply connect a 240 mAh battery with a JST cable, or use a JST-XH adapter cable to connect a 138 mAh battery, plug the Charge-o-matic into a spare USB port on your computer.
 A LED comes on to indicate charging and goes off when the charge is complete. You can leave the battery hooked up forever if you want. The Charge-o-matic will keep it topped up.

Charge times are (from dead flat) 30-40min for a 138mAH cell, and 60-90min for a 240mAH cell.
 
Schematics, board layouts, BOM... etc of the Charge-o-matic be located on this thread.