Here's something from OL2003's help system:

    Include a vCard with your e-mail signature

 1.. On the Tools menu, click Options, and then click the Mail Format tab.
 2.. Click Signatures.
 3.. Do one of the following:
Add a vCard to an existing e-mail signature

 1.. In the Signature list, select a signature, and then click Edit.
 2.. Under vCard options, select a vCard from the list, and then click OK.
Add a vCard to a new e-mail signature

 1.. Click New.
 2.. In the Enter a name for your new signature box, enter a name.
 3.. Under Choose how to create your signature, select the option you want.
 4.. Click Next.
 5.. In the Signature text box, type the text you want to include in the
signature.
 You can also paste text into this box from another document.

 6.. To change the paragraph or font format, select the text, click Font or
Paragraph, and then select the options you want. These options are not
available if you use plain text as your message format.
 7.. Under vCard options, select a vCard from the list, and then click
Finish.