You mean the Samsung Galaxy Tab? It has the Market. Perhaps the upcoming Motorola XOOM? Yep, it has the Market.

The only two exceptions I can think of are the Archos tablets and Notion Ink: Archos doesn't fulfill Google requirements, and I don't know what the problem with the Adam is. (Obviously, no-name Chinese tablets also don't get the Market, but that's not a huge surprise.)

I'd have phrased it the other way: the only two exceptions that I know of that can access the market are the Galaxy and Xoom. One of which isn't available and the other is almost a poster child for the uncertain upgrade path problem.

No-name Chinese tablets aren't a surprise, but the fact that they get casually included when people talk about ecosystem devices and sales is part of the problem.