Today only, O’Reilly is running a special on all their Pocket Reference and Pocket Guides. If you use the discount code: DD399 all Pocket References and Pocket Guides are $3.99 each.
I am a big fan of O’Reilly e-books. They are all DRM-free and you get free lifetime access, multiple file formats, free updates. What this means for me, is that I can load it on my Sony Reader for access, and also load them in Aldiko on my Droid X.