Check out this email signature. I like the link to the vCard in particular. Wish we could do something similar in Apple Mail.
Or, imitation being the sincerest form of flattery, you can just edit the one you sent me, as I have done below. You can see that the link to my vCard goes to my iDisk public folder. I had to trick it, as Apple has come up with a new URL for your iDisk, e.g. http://public.me.com/membername, that doesn’t seem to feature any obvious linkability.
This is a good time to say that I discourage people from putting their logos in their email sig, as it looks like every email they send has an attachment in it, and I sometimes search for or sort by emails that have attachments.