Some years ago, it was possible to download (for free) a comprensive statistical text from www.statsoft.com . It was great, just sat on my desktop until I needed it.
These days, you can get the same thing as an online resource, again for free http://www.statsoft.com/textbook/ .
I’ve just been made aware of something that is arguably as good, if not better http://surveyanalysis.org .
Whilst still under development, it already contains a massive amount of information, of interest to anyone who works in the advanced analytics area.