You can use Outlook Express Address Book to create a file called a vCard.
It can contain as much or as little contact and even personal information as you wish.
Once you've made one, you can put it on your web site for customers to download so they've always got your information on their computer. This includes:
* land line
* mobile
* email
* web site
* office address
* etc.
Here's an example of how I've used it on my web site:
www.wally-the-window-washer.co.uk/contact.htm