Nature: http://www.nature.com/naturejobs/channels/graduate/
Science: http://recruit.sciencemag.org/
Cancer careers http://www.cancercareers.org/
Science job: http://www.sciencejobs.com/

http://www.biospace.com is also a very nice site (at least in the U.S.).

www.newscientist.com

http://fens.mdc-berlin.de/jobs/
http://www.eurosciencejobs.com/job_search.php
http://www.findapostdoc.com/firstmain.asp
http://www.jobs.ac.uk/
http://www.telejob.ch/telejob/
http://www.novartis.com/careers/index.shtml
http://sg.dimension.jobsdb.com/career/defa...;94568234682083