Jarte is the program I use for writing. I am trying to learn how to use Scrivener, but I love being able to have multiple tabs open in Jarte, and it can also be installed on a flash drive to be used on any computer -- handy for when I'm trying to get a bit of writing done while I am at work!

I use Online Etymology Dictionary when I am trying to make sure words are not too modern for the time period I am writing.

I'll add more as I think of them!