This is just my opinion, but I think I would try to keep your introduction
letter as real and as honest as possible.
A lot of business is done 'virtually' these days, and depending on what you
propose to offer to your prospective clients, I would simply tell folks what
it is that you do, how much it will cost them, and the good and valid reasons
why they would want to choose you over the competition.
Even something as simple as:
"Hello. Please allow us to introduce ourselves (insert text here).
We are a company that can offer you (insert text here).
Should you wish to contact us, please (insert text here)."
I don't think you necessarily need to emphasize the fact that you don't have
a "storefront" business just yet. Personal contact is great, and is
generally expected in terms of follow-up I think, but there are many
successful businesses out there who never had the benefit of that personal
face-to-face to begin with.
Marketing is a tricky and challenging thing for sure, and I wish you the
very best of success for your business in 2006.
Karen