A toll-free number is something you should have on all of your sites that sell products or services.  Best practice states that you should list both a toll AND a toll-free way to call you, and to make sure that you label the toll-free number in a clear and obvious way.  Believe it or not, there are still millions of people who don't know that numbers like 888 or 877 are free for them to call. 

In fact, you should take this into consideration when choosing your toll free number - 800 is more recognizable, but also has a higher chance of being recycled and being listed in thousand of places with the "old" owners information, leading to wasted calls and extra expense for you.

A good place to get yourself a toll-free number is Kall8.  You can get a number for as low as $2 a month plus $0.07 per minute on the inbound calls.  At these prices, you should pick two or three numbers - one for inbound calls generated by advertising, one for customer inquiries, and another for testimonials from happy customers.  Take those audio testimonials and put them on your site using Audio Generator.