UC500.com

I've made this Post Sticky at the top of the forum.
If you have other good reference guides Please add a comment and I'll revise this Post.

I've noticed that many questions asked here are answered inside these guides. Best part is that it is free.

Here are all the CUE admin guides
http://www.cisco.com/en/US/products/sw/voicesw/ps5520/prod_maintenance_g...

and CME guides
http://www.cisco.com/en/US/products/sw/voicesw/ps4625/products_installat...

Cisco Press' Reference for CME and Unity Express

Big book. It is a bit dated as it does not cover the latest features in IOS or the UC520 but it is a great book and will teach you all of the basics you need for Cisco CME and Unity Express. A must have in your library if you are new to Cisco voice. Using the link here to Amazon.com helps support our site.