'Contact us' forms - websites have it and it is OK. They allow you to type a message that will be sent to an employee and the user will get an answer eventually.

Publishing a phone number helps a lot. It works great for local users. Some of them may be reluctant to long distance calls.

Toll free numbers - they are as free as you pay for them.

What is a solution then?

There are several, but there is one of them that looks very tempting. Try Google Voice! You need to request an invite to be able to sign up. It is well worth it.

After you sign up, you will need to 'link' the account to a regular US phone number. Then you will be able to create an easy web widget. Basically it will be an 'call me' button. When your client clicks on it, s/he will be able to enter her number so the widgets calls her and call you. Alternatively you can send her message to a voice mail. It is easy and free. Contact us to get such widget on your site!