Which font should I use for presentations?

Garr Reynolds/Presentations:

Serif fonts were designed to be used in documents filled with lots of text. Serif fonts are said to be easier to read at small point sizes, but for on screen presentations the serifs tend to get lost due to the relatively low resolution of projectors. San-serif fonts are generally best for PowerPoint presentations, but try to avoid the ubiquitous Helvetica.

Good to know.