The Preferences dialog (in the Window menu) lets you customize the behavior of your environment, such as when to build your projects, which target processors to build for, and how to open new perspectives.
The Preferences main menu.
Besides global preferences, you can also set preferences on a per-project basis using the Properties item in right-click menus.
On Ubuntu 9.10, icons inside menus aren't displayed if you use GTK 2.18; see bug 293720 at http://www.eclipse.org .
Workaround: Turn on the Show icons in menus option (for example, under on Ubuntu 9.10).