With its free-to-view classified listings for everything from apartments to erotic services, Craigslist has played a large role in the demise of the newspaper industry. But with free listings come irrelevant and inappropriate listings as well.

Several startups offer cleaner, more controlled alternatives, and according to Patricia Nakache of venture capital firm Trinity, consumers are "willing to pay for a better experience."

Among these alternatives are Care.com, a listing site for caregivers, tutors and nannies, and Loop.net, a real estate listing site.

Consumers pay to view the commercial properties listed for sale on Loop.net. The company had revenue of $71 million in 2007 and has 3 million paying members, according to The New York Times Bits blog.

Although users may want a cleaner alternative to Craigslist, the key to maintaining these subscribers is adding new content, Nakache said. Care.com provides additional materials, such as articles and helpful guides that keep subscribers returning even after they've found what they were looking for.