Concept Feedback is a site which allows you to upload your design or concept and receive feedback from other designers. It’s free to upload your concept and free to submit reviews - so it’s like Crowdspring or 99designs,  with only the feedback element and no prize money or brief from a client. A simple concept and a simple enough site.

From the site:
"Designed specifically for small and medium business marketers, graphic designers, and web developers, Concept Feedback provides a simple tool to get quality feedback on marketing concepts. Best of all, it's 100% FREE!"

While you have the option of posting website designs, logos, ads or flash presentations, it seems that the first two (design and logos) dominate the current submissions.

PROS

• Each reviewer has a reputation score, which helps in ensuring that the concept contributor gets the best feedback. You gain a reputation score by submitting and reviewing concepts and through the votes other users can make for your reviews (very clever!). If you submit unhelpful reviews or abuse on the site, your reputation score will go down.

• While you can get high quality feedback from members who have a high reputation score, receiving more than three reviews for your concept should help you see a trend in the feedback and you can probably take these criticisms onboard.

• This site can be very useful if you are a freelancer and you normally receive no criticism other than from the client.

• On the submission of your concept, you get to write your design problem and proposed solution so that reviewers can provide a proper crit.

The feedback that I have read so far for four or five concepts is professional and constructive.

CONS

One thing that concerns me is that users will tend to make changes according to the reviews or feedback that they agree with. Every designer working under a Creative Director knows that you sometimes have to make changes that you don't agree with and might not completely understand, until the design is finished.

A few other things I found quite clever are the featured member blocks on the home page and the fact you have to submit 5 reviews before you can upload a concept.  This guarantees new members’ involvement in terms of providing feedback, which is the backbone of the site after all.

I think conceptfeedback.com is a great site to use if you are a freelancer and feel a bit isolated in terms of the feedback that you are receiving. Try also running your designs past "real people", like your family and friends because you will be pleasantly surprised by the quality feedback and insight they can provide.

Also check out:

• When Revamping Your Website, Remember Your Users
• Taking Your Site to the Mobile Web
• Website Usability, Navigation Made Easy