I'm looking for web apps or online experiences that offer personalization options to users with the intent to improve accessibility, such as increased font-size, variable color scheme or layout (for example, always give me mobile). Thoughtful implementations would persist after users leave the site, so their desired settings would still be there when they came back.
Trello has an "Enable Color Blind Friendly Mode". It's pretty simplistic and probably not that useful, but their hearts are in the right place.
Have you seen any applications that do well with this type of offering?
This is actually pretty hard. I can think of a number of iOS apps that have accessible / "VoiceOver" modes that you can turn on. But web apps specifically that do this is challenging..
By the way it's funny that Trello includes this in their web app when their iOS app is not all that VoiceOver friendly...at least in my experience..