Z is a command line tool that helps you to cd to directories you use with just a few key stores. It manages this by tracking the directories you visit, and weighting them by how frequently and how recently they have been visited. I have been using it happily for a long time, and now I think that I can recommend it to other people. It uses a term frecent for ranking directories. z foo changes directory to the most frecent directory that matches the term foo. Frecency is a weighted combination of frequency and recency values of directories. It learns these weights while you visit directories, and makes you pretty accurate recommendations after a very short amount of time.

Here is its github page: https://github.com/rupa/z

Here is the HackerNews discussion about it: https://news.ycombinator.com/item?id=4464003

P.S: OS X users can install it using Homebrew by brew install z