Chris Maiorana has a useful post on directory local variables. The idea is that rather than putting a lot of context specific configuration in your init.el file, you can put those configurations in a .dir-locals.el file and they will be set only when you open a file in that directory.
I really like the idea of directory local variables but it has never worked well for me. That’s mainly because I usually wanted to execute some code using the eval keyword. That always causes some problems involving a stack overflow, no matter how simple the code is. Lately, I’ve been using them a lot in conjunction with Jinx, which has the nice feature of adding words to the local file or local directory in addition to the other usual options.
I find that really useful for my blogging. I can add post specific words to the post source file itself or I can add them to all posts in my blog directory. Maiorana uses then to set things like compilation settings, fill and wrap settings, and indentation styles.
If you have different workflows with different setting needs, directory local variables is a very nice way of dealing with them. Of course, not everything should go in a directory local variable. Some things apply to all your buffers and should go in your init.el but for those things that are specific to particular workflows, directory local variables are just what you need.