Many switchers to Mac OS X have the same question: "how can I customize my application toolbars?" While this is fairly straightforward in Windows, Mac OS X makes it much easier. Just open the customization menu by right-clicking (if you have a one-button mouse you can control + click) on the toolbar, then select "Customize..."
When you do this, you are presented with a dialog box that "rolls down" to display all of the items that you can add. Just drag the ones you want to the toolbar. If you find you don't want a certain toolbar item, just open the customize panel again and drag the item off the menu bar.
For more tips and tricks like these, visit the Mac 101 section on TUAW.