Here are the February, 2008 rankings of the most productive sources of recruitment according to recruiters.
Source Rank and Usage
(1)Job Boards(1.96) 100%
(2)Employee Referrals (2.22) 100%
(3)Company Web Site (2.81) 84%
(4)Temp to Full-time (5.30) 60%
(5)Job Fairs (6.07) 60%
(6)College Recruiting (4.71) 56%
(7)Agencies (5.46) 52%
(8)Temp to Full-time (5.30) 36%
(9)Networking (5.22) 36%
(10)Temp to Full-time (6.11) 36%

Other sources mentioned but with less frequency were:
Print Advertising and Executive Search.

The average number of sources utilized by participants was 6.9