It is generally best to use standard fonts that are available on the end users device.
Using too many font faces can create a confusing visual layout.
For print materials:
Serif fonts such as Times and Times New Roman are generally regarded as the most readable font family for printed text.
For web-based content:
There is conflicting information about which font is the best to use for web-based content.
Conventional wisdom is sans-serif fonts are more suited to electronic formats.
Fonts such as Verdana, Tahoma, Trebuchet MS, and Georgia, were developed specifically for use in electronic media, and are now quite commonly used.
For more detailed information on fonts, look at WebAIM's article on Fonts
These tips are based on WebAim's article "Text/Typographical Layout"
. WebAIM is a non-profit organization based at the Center for Persons with Disabilities at Utah State University.