A very nice extension for SeaMonkey is the Toolbar Buttons. It provides many additional buttons for the browser — just right click on the toolbar, select Customize and drag whatever you need on the toolbar:
Great!
This extension is also available for Firefox and Thunderbird. However, I do not use them and do not know how it behaves. I suppose it works just as well.
Great! :) Another one to my collection: https://addons.mozilla.org/en-US/seamonkey/collections/d4rkn1ght/j/?sort=name