I've been doing this for a long time, both in teaching and in writing, and what I use is:

1. MindManager (any mindmapping tool that's fast will do) - it's indispensable for starting with a framework and a plan, for brainstorming, and even for writing large chunks of text.
2. WordWeb Pro (old version) - for the pop-up dictionary
3. Copious WORD MACROS. There were just some new ones out out for free here: http://www.soltys.ca/blog/2011/05/macros-for-editors.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+CoreDump2+%28Core+Dump+2.0%29

4. Millions of Autohotkey scripts to pop up commonly-used phrases/verbs and things for me that I create.
5. Style guides
6. Evernote and CintaNotes - Cinta is lightning-fast and can tag ideas/things so that I can pull them up quickly later.
7. Chrome/Firefox and many extensions - can go into these later
8. Breevy - for convenience when Autohotkey gets too cumbersome.

I'm thinking about putting together a page for these things, so I'm happy to answer any questions or brainstorm with y'all. I'm excited about this.

Would love to see a comparison of Breevy and PhraseExpress.

Breevy continually adds new things-  did you know that you can make a folder full of abbreviations pop up as a context menu in any window for you to choose an abbreviation?