I think I saw most of y'all on the Beekeeper's Apprentice giveway thread--hi again! For any others, I help Laurie King with her forum and online outreach. My latest information is that the first four are coming to the kindle store shortly, and I'm checking on what other formats are coming as well.
Another publisher, Bantam, has books 5-8, with 9 (The Language of Bees) coming out 4/28. I notice that these are available as ebooks on the Random House site.
Here is the page for the most recent one--looks like they have them in several formats, but I'm not sure about DRM status, however. I wonder if the mobi is DRM free.