Ubuntu comes with the Alacarte Menu Editor, so you can customize your menus and add entries for applications that don't automatically appear after they are installed.
To add a new menu entry:
Open Alacarte with Applications->Accessories->Alacarte Menu Editor, or by right-clicking on any top-level menu and choosing Edit Menus.
In Alacarte's left-hand pane, choose the submenu the new entry should appear in.
Choose File->New Entry. In the New Entry window, choose a Name, Comment, Command and Icon. The Command will usually be the package name, Name is what will appear on the menu, and the Comment will appear in the tooltip that appears near the menu entry. Icons are added to the /usr/share/pixmaps directory by default, or can be chosen from anywhere in your files.
To change the order of menu entries, use the up and down arrows on the right-hand side of the Alacarte window.
To stop a menu entry from being displayed, use the checkboxes beside each entry. This does not erase the menu entry, so you can restore it later in the same way.