The result is an improved search experience that delivers results from high quality sites, leaving behind spammers, aggregators and content farms.

Blekko bases its technology on a simple tool called a slashtag. Slashtags are curated sets of web sites organized around a particular topic. These cover topics as broad as health, money, and autos, and as narrow as gluten-free and neurotechnology. Slashtags are added to search queries and limit search results to only the curated sets of sites.

With the launch of the public beta, Blekko is also automatically applying slashtags to improve results in seven initial search categories: health, colleges, autos, personal finance, lyrics, recipes and hotels. For example, searching “cure for headaches” on Blekko will provide results only from the top quality sites in the health category.

For searches that don’t fall within one of Blekko’s pre-defined categories, Blekko uses its proprietary ranking algorithms to deliver relevant results from its 3 billion page web crawl. As users create and refine more slashtags, Blekko plans to expand “auto-slashing” to improve results in more categories.

“Today is the first step in a process of building a volunteer army at Blekko that will eventually slash spam from search and deliver the most relevant results,” said Rich Skrenta, CEO of Blekko. “As the number of URLs on the web increases from billions to trillions, it will take a layer of human oversight to separate the trusted content from the spam.”

Also new to the public beta is a community platform that allows users to work together as they create slashtags. This includes group editing of slashtags and collaborative communication tools. The expectation is that as the number of quality slashtags grows, so too will Blekko’s auto-slashing of queries.

Blekko has been available on a very limited basis in private beta that began in July, 2010. More than 8,000 users from around the world joined the beta. During the beta period, users created more than 3,000 slashtags.