Merely maintaining customer loyalty just isn t enough for businesses these days. Now companies as varied as Sears (SHLD), Fiji Water and Gold s Gym want to be friends with you, too -- through online social networking sites like Facebook and Twitter. Indeed, in an effort to ensure warm feelings, some companies are even offering exclusive discounts and deals in exchange for the privilege of your friendship.

Last week, for example, Fiji Water used its Twitter feed to tell followers about a 40%-off sale on bottled water purchased through the brand's web site. Subsequent updates dropped the discount by a few percentage points until the promotion expired. Meanwhile, The Melting Pot chain is offering a free chocolate fondue -- worth $16 -- to Facebook users who try the company's free application to match up their friends. (For more current deals, see charts below.)

In fact, 59 of the top 100 online retailers -- including Walgreen (WAG), Zappos.com, Amazon.com (AMZN) and Sephora -- maintain free accounts on social networking sites, according to market researcher Rosetta. Coupon sites such as Coupons.com and FatWallet.com are also getting in on the action, creating accounts to post their latest deals and codes. (See a selection in the chart below.)

"There s definitely a business advantage to having a presence there," says Tim Ross, principal of Kendall Ross, a Seattle-based retail branding firm. "It s free, targeted advertising."

Because users of social networking sites are there primarily to connect with friends, the effort toward positioning coupons on sites is still in its infancy, says Larry Chiagouris, a marketing professor at Pace University in New York City. "It doesn t pay for consumers to go out of their way and sign up just to look for coupons," he says. But if you re already on these sites and don t mind a few extra notifications, it can t hurt to connect with companies you already do business with. After all, you might just find an extra discount on a purchase you would have made anyway.

One word of caution, however: Bear in mind that by adding a company to your social network, you re giving it access to your profile. Make sure you re aware of any privacy settings the networking site offers that will allow you to limit how much personal information the company can see.

Here s a selection of current deals:

Coupon Feeds

If you d rather not read every coupon poster s tweets, check out sites like CouponTweet.com and CheapTweet.com, which track the latest deals posted on Twitter.

• Coupons.com

  -- Follow the coupon site on Twitter or visit its Facebook page for coupons including $10 on LeapFrog s Tag reading system (regularly $50). Expires April 30.

• DealNews.com

  -- Follow the sale-tracking site on Twitter for links to the latest deals, such as a Navigon 7200T GPS unit for $250 at JR.com. (DealNews.com says that s $7 less than its last low-price mention in January.) No sale end date noted.

• FatWallet.com

  -- Follow the coupon- and sale-tracking site on Twitter for links to deals like a $75 credit for new users of the ZipCar car sharing service. Expires April 30.

• TechBargains.com

  -- Follow the sale-tracking site on Twitter for links to the latest electronics deals, like the GoGamer.com 48-Hour Madness sale on select PC videogames, with select titles selling for as little as $1.

Company Deals

• InterContinental Hotel Group s Hotel Indigo chain

  -- Each location has its own fan page on Facebook. Hotel Indigo Chicago Downtown Gold Coast offers discounts of up to 20% off for its friends and fans on Facebook. Regular room rates start at $149.

• Marsh Supermarkets

  -- Become a fan on Facebook and receive up to two free tickets (each a $30 value) for the Indiana Pacers vs. Toronto Raptors basketball game in Indianapolis on April 8.

• The Melting Pot

  -- Using the restaurant s free Facebook application to match up friends and receive a free chocolate fondue (a $16 value).

• Sears

  -- Become a fan on Facebook, and receive two $5 coupons: one on a $50 in-store purchase, and another for a $50 online purchase.

• VistaPrint

  -- Talk to the company or ask a question about its products on Twitter, and receive a link offering a discount of 25% on your order.

• TechBargains.com

  -- Follow the sale-tracking site on Twitter for links to the latest electronics deals, like the GoGamer.com sale on select PC videogames. Some titles go for as little as $1.