Where are programs for all users stored? For example, I just downloaded the latest Firefox, but I don't know where to install it to update my existing version. Any help would be greatly appreciated.

usually it would be /usr/share

Why don't you use synaptic?? The latest firefox is in Sarge so i suppose it should be in ubuntu repositories.

I did use it. I just need to know so I can run this command line stuff to get java to work in Firefox. To fun that command, I need to know where my programs are. I also need to know where Java is installed.

Thanks for the replies, folks.

You can add the blackdown mirror to synaptic, it will install java for you and the plugin too(in /usr/lib/mozilla-firefox/plugins).
deb ftp://ftp.tux.org/java/debian/ sarge non-free

You can find other mirrors at http://blackdown.org if the previous one is not fast enough. With synaptic search the package named j2re1.4 and install it.

When i install something on debian i always look first for a repository before trying something else, unless i have specific reasons.

gives you a list of installed packages corresponding to the searchKey which could be java.

gives you a list of the files installed by a package.

Where do I add this exactly:
deb ftp://ftp.tux.org/java/debian/ sarge non-free

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Whew... I finally got it to work. Thanks to you guys and pointing out where the programs were, I was able to come up with this code:

cd /usr/lib/mozilla-firefox/plugins
ln -s /usr/java/jre1.5.0_02/plugin/i386/ns7/libjavaplugin_oji.so

/usr/local and not /usr/share (though the program would still work). Take a look at this thread.