Tools 2 track free books (source: NetSpeak)

Oreilly open book
Creative common's licence
Book:"Introduction to Economic Analysis"
Internet text archive

Blogs on Free text books:
Text book revolution

Free computer & IT books

Free Tech books

one can use blogsearch for searching blogs containing e-books.
we can use 'inurl' and 'intitle' for efficient searching of such stuff in google search string...
tinyurl