Eric Barker points to a new study linking a firm handshake with employment interview success:

The authors examined how an applicant's handshake influences hiring recommendations formed during the employment interview. A sample of 98 undergraduate students provided personality measures and participated in mock interviews during which the students received ratings of employment suitability. Five trained raters independently evaluated the quality of the handshake for each participant. Quality of handshake was related to interviewer hiring recommendations. Path analysis supported the handshake as mediating the effect of applicant extraversion on interviewer hiring recommendations, even after controlling for differences in candidate physical appearance and dress. Although women received lower ratings for the handshake, they did not on average receive lower assessments of employment suitability. Exploratory analysis suggested that the relationship between a firm handshake and interview ratings may be stronger for women than for men. (PsycINFO Database Record (c) 2008 APA, all rights reserved)

The full study - which I have not read, but will certainly try to look over - is in the Journal of Applied Psychology volume 93, issue 5 released in September of 2008. If you're still in school and interested in reading the journal article, you should be able to access it through your campus library.

"Handshake" courtesy AndyRob via Flickr Creative Commons