His blog was thought-provoking. http://www.aaronsw.com/weblog/
His work on the RSS 1.0 Specification enabled richer, more efficient information consumption. http://web.resource.org/rss/1.0/spec
His work on Markdown enabled intuitive, unobtrusive formatting and structuring of information in plaintext and conversion to HTML. http://daringfireball.net/projects/markdown/#acknowledgement...
His work on reddit enabled thousands—now millions—to share online information in a social manner. http://www.aaronsw.com/weblog/rewritingreddit
His work on the web.py framework gave countless Python programmers a head-start on serving information through web applications. http://webpy.org/
His work with DemandProgress gave Americans a political voice to protect and win back their freedom and the freedom of information. http://blog.demandprogress.org/people
His work with Creative Commons promoted the freedom of information and fair use and helped inform content creators of options other than copyright. http://creativecommons.org/
Thank you, Aaron Swartz, for all the above and all the other activism and works (https://github.com/aaronsw) I haven't mentioned here. You'll be missed and remembered by many.
This guy was definitely making a positive impact in the world.