Microsoft Press has been doing a 25th anniversary book offer where they put up a free pdf download for selected books for a limited time. The December books include one that you might be interested in if you're doing network programming.
The other book this month is Writing Secure Code for Windows Vista by Michael Howard and David LeBlanc. Note that this is different than the base book Writing Secure Code. It's a much shorter update that provides content about security features that are new in Windows Vista. If you haven't read the base book, I'd recommend getting and starting with that, although it isn't part of the free offer.
The download period for these books only runs through the 24th so grab them now if you're interested.