JRE and flash plugin for Mozilla (Firefox/Iceweasel)

Currently both JRE5 and JRE6 are viable options. Install either one from the non-free section

apt-get install sun-java5-jre
or
apt-get install sun-java6-jre

link java plugin library to mozilla plugin directory, e.g., JRE6.

ln -s /usr/lib/jvm/java-6-sun/jre/plugin/i386/ns7/libjavaplugin_oji.so ~/.mozilla/plugins/libjavaplugin_oji.so

This works only for i386. On amd64 system

apt-get install java-gcj-compat-plugin

usually gives most people what they want. If it’s necessary to run sun java-plugin on amd64, a chrooted ia32 env is probably the only solution.

to have flash plugin, which is only available from the unstable (sid) branch

apt-get -t sid install flashplugin-nonfree

to use predefined priorities to automatically select one implementation of “flash”
between the multiple installed alternatives (this usually works for most people)

update-alternatives --auto flash-mozilla.so

to manually select one implementation of “flash” between the multiple installed alternatives :

update-alternatives --config flash-mozilla.so