We have featured Optical Reader Library for Windows Phone 8 article on Nokia Developer Wiki.
The library can be used for decoding barcodes "out of the box" and should do an impressive job even in Lumia devices with reduced camera specifications.
What is even more cool about the library is that both the pre-processor used for preparing the image and the decoder can be replaced. We're hoping that the community will use the task and experiment with different enhancements/decoders - perhaps to read altogether different types of codes, or to read codes in particularly poor light - or perhaps which are even moving.
Please use this thread to let us know what you think of the library, show off what you've tried, and let us know how else you'd like to see the library be improved. The more interest there is, the more likely it is that this library will receive more investment!
Kiran (Nokia Developer Wiki Moderation team)