Reddit:Upload stories and articles on reddit to drive traffic to your site or blog. Submit items often so that you'll gain a more loyal following and increase your presence on the site.
Digg: Digg has a huge following online because of its optimum usability. Visitors can submit and browse articles in categories like technology, business, entertainment, sports and more.
Del.icio.us: Social bookmark your way to better business with sites like del.icio.us, which invite users to organize and publicize interesting items through tagging and networking.
StumbleUpon: You'll open your online presence up to a whole new audience just by adding the StumbleUpon toolbar to your browser and "channel surf[ing] the Web. You'll "connect with friends and share your discoveries," as well as "meet people that have similar interests."
Technorati: If you want to increase your blog's readership, consider registering it with Technorati, a network of blogs and writers that lists top stories in categories like Business, Entertainment and Technology.
Ning: After hanging around the same social networks for a while, you may feel inspired to create your own, where you can bring together clients, vendors, customers and co-workers in a confidential, secure corner of the Web. Ning lets users design free social networks that they can share with anyone.
Squidoo: According to Squidoo, "everyone's an expert on something. Share your knowledge!" Share your industry's secrets by answering questions and designing a profile page to help other members.
YouTube: From the fashion industry to Capitol Hill, everyone has a video floating around on YouTube. Shoot a behind-the-scenes video from your company's latest commercial or event to give customers and clients an idea of what you do each day.
LinkedIn: LinkedIn is a popular networking site where alumni, business associates, recent graduates and other professionals connect online.
Ecademy: Ecademy prides itself on "connecting business people" through its online network, blog and message-board chats, as well as its premier BlackStar membership program, which awards exclusive benefits.
Xing: An account with networking site Xing can "open doors to thousands of companies." Use the professional contact manager to organize your new friends and colleagues, and take advantage of the Business Accelerator application to "find experts at the click of a button, market yourself in a professional context [and] open up new sales channels."
Facebook: Facebook is no longer just for college kids who want to post their party pics. Businesses vie for advertising opportunities, event promotion and more on this social-networking site.
MEETin.org: Once you've acquired a group of contacts in your city by networking on MEETin.org, organize an event so that you can meet face-to-face.
Tribe: Cities like Philadelphia, Boston, San Francisco, New York and Chicago have unique online communities on tribe. Users can search for favorite restaurants, events, clubs and more.
Ziggs: Ziggs is "organizing and connecting people in a professional way." Join groups and make contacts through your Ziggs account to increase your company's presence online and further your own personal career.
Plaxo: Join Plaxo to organize your contacts and stay updated with feeds from Digg, Amazon.com, del.icio.us and more.
Networking For Professionals: Networking For Professionals is another online community that combines the Internet with special events in the real world. Post photos, videos, résumés and clips on your online profile while you meet new business contacts.