Programming
I develop mathematical and scientific software. I also regularly contribute to free^{1} ^{1}as in speech, not as in beer. software that I use.
Much of my contributions can be found through my github. I am also active on various development mailing lists.
Mathematical Software

LMFDB, the Lfunction and modular form database. I develop the code running the database and write software that computes or verifies the underyling data. I am currently strongly affiliated with the character pages and the Maass form pages, as well as the images for each modular form.

SageMath, an open source computer algebra system. I reworked their complex function plotting routines, and have contributed to various parts of the main library as well. If you have sage trouble or need help reporting/fixing a bug, you can reach out to me.

phase_mag_plot, tools to visualize complex functions in sage. (Associated to my paper Visualizing Modular Forms. See also the announcement page and followup page). Note that this has now been incorporated into sage.

conreydirichletcharacters, sage/cython code for working with Dirichlet characters using the Conrey indexing system. This library is primarily written by Jonathan Bober, but I've helped maintain it, in particular when sage transitioned from python2 to python3. (I also used this code to generate data for the LMFDB).
I've contributed much less regularly to a wide variety of other pieces of scientific software, including arb, eclib, ipython, and matplotlib. These are all great pieces of software and I encourage others to check them out.
Other Software

tld: a minimal list manager for people who want to do things, but with a little flexibility. I use this behind the scenes for all sorts of things that aren't publicfacing.

simple_address_book: a minimal address book that works with mutt. It's similar to
abook
, but simpler, less featureful, maintained, and in python. 
latex2jax: a python script to turn texfiles into Wordpresscompatible html. I used this for years to write math for this site. But I no longer use Wordpress, and I've built different tooling to generate notes for this site.

Vundle: a plugin manager for vim. (Unfortunately, this is now essentially abandonware. But I still use it).