Product Review Websites for SEO?

I have had an idea after reading one of Rand's posts on the SEOmoz blog. It basically explains how Google can recognize co-occurrence of keywords close to the brand name. This is why some companies rank extremely well for keywords they are not targeting. This is because other people will be mentioning their product along with the keyword e.g. I highly recommend that you buy blue widgets from bluewidgets.com. Here Google would recognize that "buy blue widgets" is assocaited with bluewidgets.com.
There are other posts on the internet that support Rand's theory/prediction.

So my idea is, one way to mention this completely naturally would be to use websites that use reviews. It is completely natural to be able to recommend that people purchase from site x on these websites. Not only that but you can probably get some of these pages to rank for "yourwebsite.com review" which is popular in Google when researching companies. I am certain some of these websites allow a raw link to the website.

My problem is I don't have a list of these types of websites so I was wondering if anybody on here does. I am specifically looking for websites where the user can post a review.

I think this would also be helpful to other white hat link builders