One of the biggest problems I have with my personal setup is the context switch that comes from working with multiple projects. At the moment, I have probably 5-6 projects that are "active" to some degree. I obviously don't work on each of them every day, or even every week.
Its hard to get back into a project after you haven't worked on it for a while. What does each branch mean? How do I run the tests for this again? What was the thing I was actually trying to do next?
For most of these, I still don't have an answer. Simply keeping a NOTES file helps, but that only goes so far.
For me, the key help would be an Emacs package that makes it easy to switch between projects I work on. It would abstract away common tasks (such as running tests, searching all files in a project, etc) and automatically save project locations on my system, making it very easy to quickly switch to what I want to work on next. Additionally, I want this system to be friendly and extensible.
Projectile is a project management system for Emacs. There are a few things that set it apart from others. Primarily, Projectile is "modern". It has a decent test suite, is hosted on Github, and is in active development.
The code in Projectile has a quality that I like to call "shallow", but maybe "transparent" is a better word. When you read its code, it all makes sense pretty quickly. It uses @magnars' great dash.el list library, which makes most of its operations very clear and obvious.
A good project management system needs to be adaptable and lightweight, and Projectile does that very well. A few years ago, I tried to use some of the different Emacs project systems that were available. At the time, I basically couldn't figure out how to use them. Every project is slightly different. Systems that are optimized for working on a C++ project probably wont work well for a Smalltalk project.
All together, this made projectile very friendly to change and contribution, and I was able to adapt it for my needs very quickly. If you have ever been frustrated about organizing projects in Emacs, I whole-heartedly encourage you to try it.