http://lsd-pl.net/ The classic one, great research
http://java.sun.com/security/ Sun's own page!
http://www.research.ibm.com/javasec/ IBM provides fundamental research, great value and much to learn! Especially the papers from Koved et al. , unfortunately no one maintains the link list. It could be perfect ...
http://www.javaworld.com is a great source for practical descriptions about the java security architecture
http://www.cigital.com/javasecurity/links.html This page (although listed very high in Google) is just useful to sell an old old book. It was not updated since 1999 :-(
http://www.cs.princeton.edu/sip/faq/java-faq.php3 Lot's of broken links and outdated info, maybe sponsored by someone who does not want surfers to find some useful sites.
www.illegalaccess.org : Judge yourself, you are just staring at it :-)