Following the popularity of Skype, the computer-based free phone site, other services are cropping up that offer free calls.

Need a number but not near a computer or phone book? Most people balk at paying $1.50 or $2 for directory assistance phone call but not many are aware of a free alternative: 1-800-FREE411.

A Boston-based company called Jingle Networks offers the service via cell phones or land lines. There is a small catch: it's advertising supported so you will have to listen to a 15-second ad.

Callers may hear a short, audio ad when requesting a phone number, but not every single time. The company says on its Web site that it won't pass on your phone number or info to telemarketers.

Calls to 411 are among the most profitable services at traditional phone companies. Less than a year after launch, Jingle Networks claimed to have taken 3 percent of the total U.S. market for 411 calls, with 450,000 calls per day (out of 6 billion total yearly 411 calls).