ThinkingRock is described as 'Open source and multi-platform software for Getting Things Done - the stress-free productivity methodology and international best selling book by David Allan. [ http://en.wikipedia.org/wiki/Getting_Things_Done ]' and is a Task Management tool in the office & productivity category. There are more than 100 alternatives to ThinkingRock for a variety of platforms, including Windows, Mac, iPhone, Web-based and iPad apps. The best ThinkingRock alternative is Notesnook, which is both free and Open Source. Other great apps like ThinkingRock are CherryTree, Trilium Notes, Cryptee and UpNote.