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?
While not specifically an online experience, one of my previous projects included a CSS style switch for colorblind users in a console view what was basic HTML. Under the default, error messages showed in red so they could be identified quickly in a sea of stdout messages and success messages were green.
In the colorblind mode, error messages were switched to a golden yellow and success messages were blue.
The switch was accomplished just by adding a class to the main console container.