Emacs can do a ton thanks to the code that people have contributed over the decades. Here’s a list of things I’ve used Emacs for, although I’m sure I’ve still missed a few!

• Taking notes
  • Storing reference information
  • Publishing blog posts
• Programming / coding
  • Rails
  • PHP / Drupal
  • Java
  • Javascript
  • HTML / HAML / ERB
  • CSS / Sass
  • Emacs Lisp
  • Ruby
  • Perl
  • SQL
  • Bash scripts
• Managing my to-do list
• Timing tasks
• Managing my finances
• Studying
  • Dictionary (Japanese)
  • Flashcards
    • With random fortunes displayed for correct answers
    • With random images displayed for correct answers (cute kittens!)
  • Example sentences lookup (Japanese)
  • Random example sentence added to blog posts (Japanese)
• Brainstorming, outlining, and mindmapping
• Handling my mail
  • Doing mail merges or file merges
  • Tracking correspondence
  • Personalizing greetings and signatures
• Managing contacts
• Writing research papers
• Managing my bibliography
• Making presentations
  • Planning presentations
  • Delivering dynamic presentations (with executable code!)
  • Using speech synthesis to remind myself about what’s coming in the next “slide”
• Reading documentation
• Analyzing my blog and my writing
• Running a shell
• Searching files
• Cleaning up, filtering, or transforming text
  • String and regexp replacement
  • Keyboard macros
  • Custom Emacs Lisp functions
• Editing files on a remote server
• Editing files inside an archive
• Reviowing and making text notes about images and other files
• Chatting on IRC
• Chatting on instant messengers
• Checking the calendar
• Playing Nethack
• Playing dunnet and snake
• Browsing the Web
• Posting to Twitter and other status update sites
  • Rigging up my to-do list to automatically publish task data to an internal status update site
• Calculating expressions
• Using a spreadsheet
• Exploring directories
• Renaming, deleting, or moving files
• Drawing ASCII art
• Reading news
• Comparing files or revisions
• Typing in Japanese or Latin
• Reviewing similar files
• Synthesizing speech – “reading” books, technical manual, mail, etc.
• Learning more about Emacs
  • Random symbols and commands
  • Documentation
  • Source code
• ROT13 and Morse code encryption/decryption
• Editing GPG-encrypted files
• Practising typing
• Opening spreadsheets and other files downloaded from the Web
• Taking screenshots (mostly of Nethack games)
• Analyzing web logs and other files
• Calculating days between two dates
• Sending text messages
• Analyzing source code
• Interacting with APIs
• Doing weekly, monthly, and yearly reviews
• Versioning my files
• Expanding text snippets
• Drafting a book
  • Tracking my progress
• Editing files as root
• Compiling and running programs
• Editing text from the browser