Ebooks from Apress
Apress has a good reputation as a .Net publisher and they have launched a series of ebooks.
One concept I like is that you can buy the book (the real paper one) and get the free ebook version.
Also as a recent ebook entry “Foundations of Ajax“ by Ryan Asleson.
You can download a chapter here
And they also launched a mobile version of their website which is a good and appreciated idea since not a lot of publishers think about mobile computing.