Usage

USAGE and word choice
University of Victoria (great campus!) usage guide
http://web.uvic.ca/wguide/Pages/DictionUsageToc.html

USAGE and style guides
The Economist magazine has a free style guide; although it is simple, it is solid.
http://www.economist.com/styleguide/introduction
Grammar Girl web site and podcasts (despite the name, a serious contemporary usage resource)
http://grammar.quickanddirtytips.com/
MIT’s ComDor Editorial Style Guide
http://web.mit.edu/comdor/editguide/
Writing Technical Articles
http://www.cs.columbia.edu/~hgs/etc/writing-style.html
Technical Writing
http://www.rbs0.com/tw.htm
Strunk and White’s The Elements of Style online
http://www.bartleby.com/141/
The Coventry University Harvard Reference Style
Is here
Google can be a concordancer too:
http://www.johntedesco.net/blog/2012/06/21/how-to-solve-impossible-problems-daniel-russells-awesome-google-search-techniques/
You can ask questions at Stackexchange:
http://ell.stackexchange.com/questions/44976/types-of-books-or-types-of-book
Google ngrams are a pretty cool tool:
https://books.google.com/ngrams

USAGE: Concordance
1. Fantastic! Two great concordance samplers which can access the biggest and most famous corpuses (including the British National Corpus) are:
http://www.lextutor.ca/conc/eng/
http://corpus.byu.edu/
2. Laurence Antony at Waseda  University made Antconc, a free software for making your own concordance!
http://www.antlab.sci.waseda.ac.jp/antconc_index.html
http://www.antlab.sci.waseda.ac.jp/software.html

Journalistic style:  the 4-box system
http://www.mcgillreport.org/largemouth.htm#anchor4