The October 2009 Usability News Newsletter has a great article highlighting a recent typography study on Web font faces.
Know Your Typefaces! Semantic Differential Presentation of 40 Onscreen Typefaces
This article presents results from a study investigating the personality of typefaces. Participants were asked to rate 40 typefaces (from serif, sans serif, display, and handwriting classes) using semantic differential scales. Responses are shown by typeface class and individual typeface using scaled scores. These results are helpful to practitioners when deciding which typeface to use for online text.”