In February it was 200ish, in April it was 325ish, and now it’s around 370 Microsoft Press ebook bundles available. Take a look. When you see an e icon in the Ebook column, the title is available is four different electronic formats.
Here are more details:
Nothing free available?
ciupaz, click the ebooks tag and you'll find plenty.
It's seems that these links go to the buy page at O'Reilly, ma nothing very free indeed.
DRM free is what the title said. Which is... not so bad.