Draw animations in What now?

I'm at the point where I need to make some decisions on how my sprite editor is going to work. First I need to decide how my artwork is going to be formatted. My first plan is to have a large image broken up into a grid, with each row in the image corresponding to a specific animation.

I need to figure out how I'm going to draw that animation first. I want something free and easy enough to use. I've found a couple of free 2d animation softwares that I'm going to investigate.

• Synfig Studio - Looks like a pretty well featured 2D animation application
• Pencil - The examples don't look as pretty as Synfig, but I'll check it out as well.
• Gimp Animation Package - It's an add-on to gimp. It's kind of a hack, hard to work with.
• Creatoon - Apparently it used to be a commercial package, but is free now.