Where do you install applications in Ubuntu which will be accessible by all users?

"but in Ubuntu its usually stored in the users local directory.

Hmm. This isn't really true (or I misunderstood what you meant). Usually programs are installed using Ubuntu's package management system (deb packages), and they are available system-wide for all users. This is by far the preferred method of installing software.

When (on rare occasions) installing something outside the package management system, I tend to use /usr/local/programs, and create specific subfolders there for different programs. Often, I'll also put a symlink (or simple startup script) under /usr/local/bin to make it easier to launch these applications. Of course, /opt or any other location would do just as well, as long as you make sure all users can access the files and directories (as Bobby pointed out).

If you want such programs to appear in the start menu of your desktop environment, you'll need to take care of it yourself. E.g. this shows how to add entries (for one user?), assuming you use Gnome. I'm sure there's a way to add it for all users, but off the top of my head I'm not sure how; maybe others can help you there."