It's early days yet, but I thought I'd post a link to my wee project -
It shouldn't need too much explaining - it's a simple way to create a theme by dragging and dropping blocks on to the page, choosing colours, and various other options. Then just download it! You can simply add it to your site to start using right away, or use it as a base to customise until you've got exactly what you want.
At this stage, I'm not promising it'll all work perfectly - I'm just working on it, and little by little adding new features and fixing bugs.