Access Firefox is very cool. The website is maintained by Ken Saunders, who is legally blind. He is able to enjoy the web thanks to wonderful accessibility support in Firefox.
The site links to large and high contrast themes, as well as extensions that can read text out loud, mouse gestures, and web developer tools that can customize web pages for super easy viewing.
Metal Lion 300 is a cool theme that can bundle with the Metal Lion HiViz Sidebar, a tool to tweak how text is displayed.
There’s also the big ass theme Kempelton Large.
I just had to try it out. And that made me look for other large themes.