Of the 800, more than 100 are from Microsoft itself. Depending on your point of view, this could be either a good or a bad thing. Good that Microsoft is making sure its own stable of programs, from Business Contact Manager to Zoo Tycoon, work with Vista. Or bad that Microsoft's own apps (including every individual piece of the Office 2007 suite, listed out separately) comprise more than an eighth of the list.
Who else has apps on the list? Many of the usual suspects. Surprisingly, Google has a few, including Google Desktop and Google Toolbar, which are designated as "works with Vista" apps.
Who is noticeably missing from the list? Adobe, IBM, McAfee, Symantec.