So you think you're doing everything possible to grow your business? A new report suggests otherwise.

Many small businesses are not taking advantage of cheap (or even completely free) online tools, according to Citibank's small business survey. The bank quizzed 552 executives across the U.S. at companies that posted revenue of more than $100,000, and employed 100 or fewer workers.

For example: The buzz around social media is deafening, but a whopping 81 percent of respondents say they still haven't tried it. Why not? Nearly half of respondants (47 percent) don't believe that Facebook, Twitter, and LinkedIn are of value to their business, another 21 percent think the sites are for personal use, and 18 percent say they don't know enough how to use the sites. (To read more about how social media can help – and how Inc. 500 CEOs use it aggressively – click here. And if you fall into the category that needs a primer, click here.)
Younger executives tend to be slightly more plugged in to social media – but the gap is hardly a gulf. According to the survey, 27 percent of those business owners under age 45 had used Facebook, LinkedIn, or Twitter in the past year, compared to 16 percent over age 45. 
Other online tools that are going unused: Nearly 40 percent of small businesses surveyed don't have a website, 62 percent don't send marketing e-mails to promote their business, and 84 percent haven't engaged in e-commerce. But among the companies that do have a website, 74 percent say it's an effective way to bring in business. 

"Many small businesses today have yet to really harness the marketing and communication power that online tools can provide them," said Raj Seshadri, Citibank's head of small business banking. "Our survey reveals a huge opportunity for many businesses to begin using some of the basic online tools, such as email marketing, to drive their sales."

The small businesses surveyed also have been slow to adopt other methods of online marketing. Two thirds of small business aren't buying online ads – or using search engine optimization.

Again, younger survey respondents were more likely to have taken advantage of other web tools. Four out of five (81 percent) under age 45 had used a web site for marketing, compared to 69 percent of executives over age 45. Fifty-two percent of the younger crowd had tried search engine optimization, compared to 35 percent in the older group.

What do you find to be the best online tool to promote your business?