Since its launch in April 2007, the number of reviews and products offered on Buzzilions.com has tripled. Today, the site offers more than 400,000 reviews on 125,000 products from over 1,000 ecommerce sites. PowerReviews says that the traffic driven through Buzillions also converts at nearly twice the rate of other shopping portals. In April we compared PowerReviews to Bazaarvoice and other competitors – PowerRevies main advantage is easy integration, and a free version of the product.

User generated reviews help sales at ecommerce sites, but few startups have the technical and product resources to build this internally. PowerReviews, Bazaarvoice and others have stepped in to fill this need. Aggregate Knowledge and Loomia address different needs in the ecommerce space – helping these companies merchandise and recommend products to users based on behavior.

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Texas-based Bazaarvoice provides white label Amazon-like editorial recommendations for products to other companies. The pitch is that it is cheaper for companies to use Bazaarvoice’s setup than build their own client in-house.

Other Bazaarvoice products include SyndicateVoice, a program where Bazaarvoice brokers relationships with leading shopping comparison engines — such as Smarter.com, Google, MSN and others syndicating clients’ reviews to these sites with links back to the retailers; and Ask & Answer, a white label community-driven Q&A for any product or service page.

Current BazaarVoice clients include Wal-Mart, Dell, QVC, Sears and Macy’s.

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What this article didn’t mention is that Austin-based Bazaarvoice, a company I covered just over a year ago, is the technology and service behind Walmart’s new features.

Like Aggregate Knowledge and Loomia, Bazaarvoice provides services to ecommerce sites that they may not be able to, or want to, build themselves. But where Aggregate Knowledge and Loomia provide recommendations, BazaarVoice offers user generated content features like comments, ratings and reviews.

Getting such a large etailer is a major milestone for them. BazaarVoice isn’t the sexiest startup, but it has a real revenue model and is clearly seeing some success. It was funded by First Round Capital and Tom Ball at Austin Ventures.

See our coverage of Buzzillions as well, a BazaarVoice competitor (albeit targeting smaller ecommerce sites).

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Menlo Park-based Aggregate Knowledge, led by CEO Paul Martino and VP Products Chris Law, launched officially today at the eTech conference. The company creates automated “behavior recommendations” for websites – things like “people who look at this also looked at” and “people who bought this also bought” features. See screen shot here for a visual. Integration is extremely simple.

Aggregate Knowledge also creates white label “ajax homepages” for clients that help to promote this information. See this screenshot for an example.

Texas-based BazaarVoice, which is a little further along than Aggregate Knowledge, provides Amazon-like editorial recommendations for products – things like customer reviews, etc. This is big business – BazaarVoice is able to provide their service at a fraction of the cost of in-house development, and even very large sites like CompUSA are starting to adopt their solution. Pricing starts at about $2,000 per month for smaller customers. In addition to Josh Kopelman, BazaarVoice has received funding from Tom Ball at Austin Ventures.