One way to get into SMB accounts is to take over their appointment calenders. This is an approach that has been embraced by a growing horde of start-ups …. at least 10 by some counts.

Silicon-Valley-based BookFresh, formerly known as HourTown, has raised $1.5 million from NBC Universal, Baseline Ventures, Hatch Ventures, Ron Conway and others. The 10-person team calls itself “The OpenTable for Eveything Else” (besides dining) and is trying to stick out from the crowd with a platform that can easily be added as a widget to SMB sites, and marketed via partnerships with publishers.

Like others, the site offers free basic listings to SMBs, and has developed three tiers of paid services: Business, at $19.95; Pro, at $29.95; and Enterprise, which has variable pricing. Among the myriad features are transaction processing, search optimization and support for multiple staff. The ultimate goal is to launch a directory of high-quality merchants.

During the past two weeks, BookFresh has announced partnerships with TypePad, the blog platform providers, and with Homethinking, a site that offers tips to home buyers while helping Realtors showcase their listings across the Web, offering free syndication to sites like Craigslist, Trulia, Zillow and others.

An example of Homethinking’s implementation is here. Using the site, home shoppers can browse through various Realtors, review their performance history, and then book an appointment online at their convenience instead of having to line up a time via e-mail communications.

“We’ve seen tremendous uptake of the feature in our beta testing and agents are finding great value in allowing live appointment scheduling,” says Homethinking Founder Niki Scevak.

BookFresh CEO Ryan Donahue, a PayPal vet — an alumni group that includes Jeff Jordan at OpenTable and Jeremy Stoppelman at Yelp — acknowledges the current glut in appointment services. But he thinks he has an edge over rivals. “We’re not a consumer destination,” which try to be marketplaces onto themselves, he says. “We are exclusively focused on the SMB owner. We’re hammering away on the merchant acquisition problem.”

The key to really understanding the business is seeing appointments are the flip side of leads (something I also heard from an SEO coach at the recent TargusInfo Leads Quality conference). Appointments share many qualities with the leads market, but also have some real advantages.

“It is a highly qualified flavor of lead, with a natural connection to both buyers and sellers” says Donahue. “The critical differentiator is that leads are typically non-exclusive where as appointments almost always are.”

They also have a high degree of commitment because the buyer and seller are promising to be somewhere. “It is an interesting social contract,” he adds.