ToDo lists. I find that when I get bogged down for any reason, if I create a todo list of items that have to get done I'm more likely to do the items on the list. I tend to pick up momentum as I cross items off the list. Make the list a manageable size, finish it off and create a new one. For product related tasks, getting actual users and feedback from them is a huge motivator as well.
http://www.43folders.com/2005/09/12/building-a-smarter-to-do...
http://www.43folders.com/2005/09/13/building-a-smarter-to-do...
http://lifehacker.com/270404/the-art-of-the-doable-to+do-lis...
and my personal spin: