- From a blog post some months ago (sorry--can't remember where) I collected an Excel template called the "Writing Marathon Template": http://www.zokutou.co.uk/tools/. It's satisfying to see the word count mount up, and the template scolds you ("you'll never finish at this rate!") if you don't meet your goal. [Updated to add: Here's the home page:]http://www.zokutou.co.uk/tools.html
- PowerProf suggested the Egg Timer some months back, and it's great. Setting the timer for a specified time helps with the "getting started" process of writing. There's a free version, but the $5 spent is well worth it.
- Clockworktimer.com is an online timer that helps you to track your productive (and not-so-productive) activities.
- There are probably lots more online toys for these purposes, but lifehacker.com just had a post about one that I've used for a long time: a paper appointment book divided into 15-minute segments for tracking what you're doing.
- Another paper favorite: the trusty old steno notebook, with each page divided into 4 quadrants: Write, Read, Respond, and Do.
Of course, the irony is that when the writing is going really well, these are all superfluous because you lose all track of time and just want to keep going.