I (re)built a straightforward web interface for geocoding addresses in a CSV (or other delimited text file) and automatically visualizing the results on a map: https://emanuelfeld.github.io/geocoder/
Just upload your file, selected the address column(s), and give it a go. The end result is a file with additional latitude and longitude attributes, available in CSV and GeoJSON formats.
Most GIS applications are overkill for geocoding and other options don't allow for a quick visual sanity check of the results, hence this tool.
At the moment, I'm plugging into Google's geocoding API, which means a 2,500 address limit per IP, per day. More information available here: https://emanuelfeld.github.io/geocoder/about
If you find it useful for your Code for DC project (or otherwise) or wish it had some additional feature, please do let me know!
Emanuel Feld
Note: I used to have this up as an RShiny app, but RStudio kept shutting it down for overuse and, anyhow, now it's much more functional.