Here's a great article from A List Apart about staying motivated.

There are some good ideas there, and I think I've probably used them all. The hardest thing I've found is noticing that I've lost my focus and my appetite for keeping going. If you haven't realised that you've lost motivation, you're unlikely to do anything about it :-)

I'm getting better at it - I just have to keep trying to spot when I'm spending too long re-checking my email, or "just having another quick game of minesweeper"...

Obviously, I think tedium can help out with some of these motivational tricks:

Set goals
Writing down your goals is a great way to remember what they are...
Stack the deck
Only giving you one line to describe your task was a deliberate decision. It forces you to keep your tasks small and achievable. Divide and conquer is the mantra for the day.
Retreat, but don't surrender
If you use tags to let you focus on your current project, then you'll automatically be ignoring everything else (until you decide to come back to it).
Follow your progress
This is something that we think is missing in most todo list applications, and something we're trying to do with tedium. We leave your completed tasks visible for a while so you get that instant feel-good from crossing things off, and at the top of each list of tasks we give you fun one-liners to show your progress.
Work through it
When you just need to grit your teeth and get on with it, I find my todo list comes into its own.

Now what are you doing still reading this? Get on and do something!