The first app that I saw through to "completion." This project was a tag-team effort between myself and a fellow Magic: the Gathering (MtG) aficionado and collector @shynonagons. It could still use a lot of work, of course, but the main functionality is there. There're just better implementations out there (one, at least) that preclude me from continuing work on it. To toot my own horn a bit, though, the card search UI is still better than any other search UI I've found out there for MtG.
On the site you can search cards and build decks, share them with friends, make them public or private, and also enter your collection. While still fully operational, the URL has officially been relegated back to its Heroku host here.
Exarch's back-end is NodeJS with ExpressJS. It uses MongoDB for the database layer. On the front-end it uses Create React App with styled-components for styling goodness.