The 'i2c_iox' Library. This library is for both 8-bit and 16-bit I2C I/O expander devices. I posted the library on google here:Google Code Archive - Long-term storage for Google Code Project Hosting.
I've only tested the library with a Texas Instraments PCA9539 (It's the only device I have at this time). The library has been working with the tests I've ran so far. I do welcome any feedback from others who'd like to test it as well. In particular I could use feedback from people with 8-bit devices, or even better, those with both 8 and 16 bit devices. The example sketch is setup to use one 8-bit device and one 16-bit device at the same time. See the included readme.txt file for information and instructions on how to use the library. I hope others will find this library usefull.
Enjoy! [smiley=thumbsup.gif],
DigitalJohnson
update:
It's been a while since I posted this library and I was hoping to get some feedback on it. :0 The web page shows 17 downloads to date (I was one of them(DL test)). I know that's not many. 
However, would one of the 16 people that downloaded it, please tell me what you think. I'm always looking to improve my coding skills. Maybe you'd like some feature added or can suggest an improvement to my code. The way I see it, everyone here can learn something from everyone else on this forum at some point. So speak up! 
Thanks to those who DL'd my library. 
I hope it's useful to you. 