WordPress is the worlds biggest bloging platform. I'm currently in the process of improving there RSS and Atom support.
AntennaPod is an open source Android podcast client. I've made quite a lot of contributions to AntennaPod but they mainly revolve arround the parsing and consuming of podcast feeds (RSS and Atom).
I've helped Mozilla follow defined standards related to publishing and advertising podcasts with there debut into podcasting.
Syndicated Media is an organisation with a goal of making podcasts better. I've helped write the technical specifications that they aim to use in order to advance podcasting.
Fireside is a podcast hosting company. I've helped them understand the fundamentals of podcasting: RSS.
Feed Validator is a very technical piece of software that's designed to detect a wide range of issues with feeds, I used my knowladge of the standards to identify some of it's rules that were against the RFCs
I'm currently in the process of improving there Atom API to better follow the specification.
Hugo is an bloging platform. I'm currently in the process of improving there RSS support.