The first method of logic level shifting uses a transistor to do the level switching and an inverter to correct the polarity. The circuit was put together on a bit of old PCB substrate using SMT components, superglue and a dremel. See the blog post for a bit more detail.

http://blog.swan.id.au/index.php?entry=entry091211-084251

This is the improved level shifting circuit. I found this in an application note by Philips (AN97055). This can be used for shifting between pretty much any voltage levels so long as your FET is appropriately specified. If you are doing a particularly low voltage on one side, make sure Vgsth (gate source threshold voltage) is sufficiently low (recommended at least 1V less than the lower of your two voltages). The Philips app note provides all the design detail necessary to implement this circuit. I still think this sort of thing should be available in a single chip that just takes the two voltages you are shifting between and provides a number of channels... if you know of such a device, please let me know.

http://blog.swan.id.au/index.php?entry=entry091214-132330