As a software developer, I regularly scour the web for free e-books in order to suppliment my collection of reference materiel for my profession and to further extend my limited budget. Here are my latest finds and updates to links for books I (or others) may have posted previously. Some are books targeted specifically for the developer audience and others have a much broader application. Hopefully you will find something useful, enjoy!
Eric Ligman has posted two collections of free ebooks on his blog. Some of the titles are the same as those listed above but there are quite a few additions as well. Some are extended white papers, but valuable to the right audience nevertheless.
[update: added sample book titles for link to Eric Ligman's blog.