Tiresias is a family of fonts designed for the visually impaired. It aims for maximum legibility by making all the letters as distinct as possible, which of course makes it good for everyone. Tiresias was the blind seer of classic Greek literature. It looks like this:

Note how well Tiresias discriminates between commonly confused characters:

If you already have it installed, all the type on this page will look similar. It is the default font for my website.

It comes is several variants: PCFont is for people with poor vision to use on PC screens using large characters. Screenfont is for TV screen captioning. Infofont is for public terminals such as ATMs using large characters. Signfont is for preparing signs for the visual impaired.

You can buy the Tiresias family of fonts on-line at Myfonts.com (BitStream) for $24.75 USD each.
You can buy them direct from Tiresias.org in England for 20.00 GBP each.

My main complaint with ScreenFont is that O and 0 are not distinct enough. The Tiresias fonts with a 'Z' after their names distinguish between the 0 and O by crossing out the 0 (zero). The letters have quite conventional shapes, unlike my proposed Proofreader font which has a similar purpose. The other problem is left and right quote look the same: “ ”.

The kerning in TiresiasScreenFont needs some work. Combinations like CO CC CP CE are hard to make out because the letters are too close together. These errors don’t cause much trouble except in Forté Agent Newsreader where they cause the rendering to sometimes go so totally screwy that you can’t continue editing.

The creators of the font has this to say about my complaints with the font,

Tiresias Screenfont was originally designed for subtitling use on digital television. It was designed for legibility at television viewing distances and constrained by space and resolution. So due to the scaling restrictions on TV screens, it was not designed for the intention of ever being used at small point sizes. We are aware there are a few kerning pairs (spacing between letter combinations) that still need rectification so we have noted your suggestion.

You can read what BitStream has to say about the font.

You can download a free copy of Tiresias Keyfont V2, a font for labelling keycaps.

I highly recommend getting a copy of Tiresias PCFont Z. It makes working with a computer so much more relaxing. I can’t think of a cheaper investment that has such high returns in comfort.