Valfarly chanced upon wikipedia and thought "that'll never work"... but after using it a few times, he eventually got sufficently annoyed by a typo to do something about it and on 15th March 2004 hit edit. From there it was a slippery slope to writing articles for things he found no-one else had written about and adding tidbits, factoids and other nuggets of information to previously covered topics. Finds himself correcting spelling and grammar far too often!
You can install user scripts written in JavaScript to add helpful features to your account, and to automate various tasks. You could write your own scripts. But many user scripts have already been written by Wikipedians, and they are ready to be made use of. To enable these scripts, simply copy and paste them into your common.js file. (Only logged-in users can install scripts). This will allow use of the script in any Wikipedia skin (Vector is the default skin).
Watchlist sorter – Sorts your Watchlist by namespace, and shows the pages for each namespace in alphabetical order. Also adds spacing for further ease of reading.