I haven't seen this posted and came across this site a few days ago. I had a dead tree version of one of the books they published and noticed at the back there was an offer to also obtain the ebook version for an additional $10. Once on the site I noticed that Apress.com has an ebook of the day special. These books which are normally up to $45 are available for one daily only for $10.
About Apress:
"Apress is a technical publisher devoted to meeting the needs of IT professionals, software developers, and programmers, with more than 700 books in print and a continually expanding portfolio of publications. Apress provides high-quality, no-fluff content in print and electronic formats that help serious technology professionals build a comprehensive pathway to career success. "
Their books are also available via Safari online subscription services.
URL:
http://www.apress.com/info/dailydeal
The only downside is that you have to check daily. So far I haven't seen a way to get the current ebook specia info delivered to me on a daily basis.
Ellen