Problem: Java JDK/JRE 6 is installed on my Windows 7 system, but the Java Plugin is not installed in any of my browsers. What gives?
Solution: My guess is, the installed browsers (Firefox, Chrome, IE, Seamonkey, Safari) are all 32 bit versions. So the 64 bit Java installer does not update them.
To solve the problem, just install the 32 bit version of Java 6. This installs the plugin for all the browsers. You end up with Java in the following locations:
c:\Program Fiels (x86)\Java
Just put the Java of your choice in your path and you should be good to go.