There is a new Geoprocessing menu in version 10.0, illustrated to the left. The upper part of the menu contains 6 geoprocessing tools. The lower part contains actions that open other windows, such as Search For Tools which opens the Search window, and ModelBuilder which opens the ModelBuilder window. We've gotten a number of questions about the 6 geoprocessing tools listed in this menu.
Yes—just follow the instructions in the Desktop help topic Adding and removing tools on menus and toolbars. You can add any tool to any menu, including model and script tools that you create. And you can create your own menus and add tools to them. For example, below is a menu I created called "My Tools". It has three pull-right menus: Fields, Create, and Copy. In the Fields pull-right menu, I added the three field tools I use most often: Add Field, Delete Fields, and Calculate Fields.
As you can imagine, choosing which tools to include from the hundreds available was a source of endless debate within the geoprocessing team. We based our final decision on tools that appeared in some of our past software, such as ArcView 3. The fact that you can customize the menu made our decision somewhat easier, but angst-ridden nonetheless.
When you customize your menu with geoprocessing tools, you are gaining access to your most frequently used tools. If you want to access your most recently used tools, open the Results window. If you haven't used the Results window in the past, be sure to check it out—it has a lot of powerful functionality as describe in the post The Power of the Results Window.
You can do more with the user interface besides adding geoprocessing tools. See the Desktop help topic About configuring the user interface for more information.
As mentioned above, you can create your own custom menu and add tools to it (or simply add tools to the Geoprocessing menu). Another method is to create a custom toolbox and add your favorite tools to it. If you create your custom toolbox in the My Toolboxes folder, it will be readily available for all your projects. Here are the steps: