SourceNote is a new (to me?) app that makes it really easy to file away a bit of text without interrupting your current work flow.
SourceNote runs in the background, allowing you to press Copy (⌘+C) twice from any application to save a permanent note without interrupting your train of thought
For most, git provides a great historical perspective of your commits. However, it does lack iterations of code which were never committed.
As the name suggests, it bills itself as a developer tool, but was helpful even as I wrote this post.
At $3.99 it is a bargain.