The Kindle and the Sony Reader(s). The Kindle doesn't support mobipocket (at least, Amazon doesn't want it to

And as for miscellaneous handhelds, they support pretty much every format out there, with the exceptions of LRF and EPUB.
As for the iliad, gen3, bebook, hanlin v3, I doubt their combined sales make up even 20% of the market, at least in the US.