This is a Flash extension, but I think it’s valid to post it here because I still work with it. It’s a great tool for animators, and it’s a pity that since CS3 Adobe didn’t make any great improvements to Flash as an animation software.
This extension allows you to move objects in small increments that you can define with “04_set amount.jsfl”. The only bad thing is that each movement is an action, differently from using the arrow keys which you can press several times and Flash will count as a single action. It’s very simple but I use it frequently when I want to be very precise.