What is great about this method is that all of the future work has been done for you. When someone contacts me with interest in the website all I have to do is copy that website "demo" to a new domain, change the business name, and I'm on to the next project. Not only have I gotten paid for nothing, but I have received a trusting client that will use more of my services.
Believe it or not, I have found direct mail to be my least successful marketing method, but don't let this discourage you. The mailings that I have done in the past were not very targeted, and not nearly as extensive as some of the other methods on this forum. Never send anything that looks like spam, poor-quality, or confusing - it will get thrown out immediately. If it doesn't look like something you would read, chances are your potential clients aren't going to read them either.
Before jumping into direct mailing realize that you need some upfront funds for printing, packaging and shipping, but most of all you need time. It takes DAYS to complete one of these small mailings by yourself, but if you put in the time you are nearly guaranteed to see at least some results.
The last thing I'd like to note is that if you are encouraging your prospects contact you through the phone it is very important to be a good talker. When marketing your business, no matter what methods you choose, you are simply trying to generate leads. Getting 20 phone calls from interested clients isn't going to do you any good if you can't get them to sign the dotted line. They want your service, don't be afraid to provide it to them.