It's strange, but a simple text file always served my needs for TODO lists, even including notes and other information related to the TODOs. It is not pretty, but I do not have trouble finding my TODOs amidst the rest of the noise, since I am consistent with my left-side "start of a TODO line" and "start of a subTODO" symbols. Sometimes I think that having a neat, pretty TODO list program would be nice, but I learned that I find my text files much more portable (Notes on iPhone, a txt on Mac, txt in linux, txt on my Windows desktop).