In my current postdoc, I am gaining proficiency with various computational languages, environments, tools, and packages, including: command-line, Vim, Git, SVN, Python, MPI (Open MPI, MPI4Py, MPICH), and C.
Previously as a math postdoc, I would regularly use Sage and LATEX for mathematical experimentation and dissemination.
Off and on, I dabble in CSS and Javascript. In particular, check out my web-programming projects below.
Web Programming
Graph Property Database
Just a prototype; I hope to develop something like this into a slick educational tool:
My early experience with CSS and JavaScript began with manipulating other people's open-source code to make a custom version of their creation. For example...
2048
I've made two variants of Gabriele Cirulli's 4x4 tile game 2048:
256 is a 3x4 version allowing for shorter play-time.
512 is a 4x5 version with an obstruction in a center tile, which encourages a more mindful play-style.
The Tree of Mammalian Life removes the clutter of distinct leaves for different species that share a common name, yet is more comprehensive with respect to basic names used in common speech.
Sharing the Joys of Code
The following are some fun ways to learn algorithm development or practice coding.
More can be found at the Programming Games Wiki.
Online
Blockly [visual programming environments: from educational games to app development tools]