CS Review is a fantastic new service from Adobe implemented into Creative Suite 5.
It is available in Photoshop CS5, Illustrator CS5, InDesign CS5, and Premiere Pro CS5. It is so much easier to use it instead of creating Pdf comps and sending them to your clients.
The main purpose behind CS Review is to quickly share your design ideas with your clients or colleagues and you can do it straight from within Adobe Photoshop (or other applications as mentioned above)!
CS Review is a part of CS Live Services introduced by Adobe with Creative Suite 5 release last year and it is a complimentary service for a year. You just need to sign up with your Adobe account (which is Free as well).
Have a look at the interesting article that I found online and read it through. It explains how to work with CS Review and it guides you step by step. Here is the link:
Speed up Photoshop Projects using Adobe CS Review by Jacob Cass.