I've been a huge fan of
RoughDraft for several years now. I reckon I've written upwards of 150,000 words using it. I first found it when I was searching for a program that would help me write a short screenplay, but RoughDraft has several other modes. It was created by a writer,
for writers. It doesn't have many bells and whistles (you can't insert tables or pictures or such), so it's pretty small. But it has the features most writers would need for most writing projects, be they prose, screenplays, stage plays, whatever. It's got the word counter, spellchecker, dictionaries/thesauri (WordWeb), find/replace, clipboard, etc.
The best feature, in my opinion, is the side panel. The side panel is an area to the right or left (you can move it) of the main window. There are four tabs: Files (which will let you access any file on your computer), List (keeps track of your Find results), Ins. (Insert - lets you insert AutoWords, special characters, and clips from your clipboard), and Pad (simply a place for notes). It's the Pad that I love so much. The Pad file is saved along with your main file and opens with it, too. So they're always together. I use the Pad for all kinds of things - when something pops into my head as I'm writing, a question or problem, I make a note of it there.
There are a few annoying things about RD. Chief among them is the inability to insert a page break. This is only a minor annoyance (to me) though, because if I need a new page, I can simply create a new file. You can have as many as 100 files open at a time as tabs in RD. For most projects, I would just create a new file for each new chapter or section.
Another thing that's not an issue for me, but would make RD very unnattractive to some of you - no Mac or Linux version.
Oh, and if you already have RD 2.11,
RD 3.0 just came out last month. Got some improvements, including the ability to print multiple copies of a single file. Finally!
And last but not least...it's free.