direnv is an environment switcher for the shell. It knows how to hook into bash, zsh, tcsh and fish shell to load or unload environment variables depending on the current directory. This allows project-specific environment variables without cluttering the "~/.profile" file.

To use it, follow the Setup section in either direnv(1) or at http://direnv.net/ to add it to your shell rc file. From there, create a .envrc file in any directory - more usage information in both the man page and website.