I was searching for a cheap and quite efficient way to power 3.3v circuit from a li-ion battery.
I found [Maxim AN438 which is very interesting.
I think it can be a good start for a 3.3v li-ion psu breakout and a good addition to li-ion charger breakout. Maybe adding a auto-shutdown circuit also.](Mixed-signal and digital signal processing ICs | Analog Devices)