A growing number of small-business owners are tapping into a vast array of social-networking tools to gain new customers, connect with their peers and share advice about common problems.A host of networks, blogs and forums for small-business owners have sprung up over the last year, with several small start-ups joining the ranks of established sites like LinkedIn, Facebook, MySpace and Friendster. Visitors use the sites to post questions and answers, make connections with distributors and suppliers, hunt for employees or show off their products for potential customers. Visa ( V) recently launched a small-business network on Facebook, which now has more than 80,000 small businesses as members. Visa is offering $2 million in advertising credits for small-business owners who join. The credit-card company says it wants the network to become a "one-stop resource" that can "empower small business owners to expand their customer base, manage their business better and exchange ideas with other businesses and trusted advisers." Bank of America ( BAC) also launched a small-business online community last fall, which now has 16,000 registered users. The site features threads, articles and forums with special guests. For instance, stationery company owner Bonnie Marcus in late May answered questions from readers about how she turned her job as a wedding planner and event coordinator into a successful company. Bonnie Marcus Collection now sells chic invitations, note cards and holiday cards to over 1,000 retailers, including Saks Fifth Avenue ( SKS), Bloomingdale's, Barneys and Kate's Paperie. Bank of America spokeswoman Tara Burke says the forums are popular with site visitors, who run the gamut from customers to browsers who happened to pull up the site on a Google ( GOOG) search. They often use the site as an resource to glean information from more experienced business owners. The most popular threads on the site relate to funding a start-up, effective branding, inventory tracking, the meaning of success, how to fire a customer and how to cut costs in tough environment.