The roadmap and ticket tracker are available on the website:
There are lists of goals and tasks on the website:

Roadmap:	http://www.dogcows.com/yoink/roadmap
Ticket Tracker:	http://www.dogcows.com/yoink/report/1


Other than that, the itself code is documented with stuff that needs doing:

FIXME marks a known bug and/or broken, incomplete code.
TODO  marks code that could use some refactoring or possible new features.