7. Type-ahead search
Glims provides an option hidden within the 'Misc.' section of its preferences: 'Auto select browser search banner'. What this means is Firefox-like type-ahead search. Just start typing to search within the current page's content, rather than messing about pressing Command+F first.
8. Alternate search engines
Glims by default dumps a load of extra options in Safari's search field, offering far more than just Google. Each engine can have a shortcut assigned, and the list is extensible via the Search Engines section of the add-on's preferences.
9. Keyword searches
Inexplicably, Safari has yet to integrate keyword shortcuts and searches, but several add-ons offer this functionality. Saft ($12) provides the most intuitive means of adding such searches (along with dozens more features), via a Control-click.
10. Grab web video
CosmoPod (€8.90) enables you to grab video from the web and convert it for iPod and Apple TV automatically. All you need do is click the toolbar button when CosmoPod finds a video and it does the rest. It can also rip audio from online video.
11. Post to Twitter
Thurly (free/$4.95) can be used as a quickfire means of shortening URLs and also posting to a Twitter account. Register the app and you can work with multiple Twitter accounts and use Thurly's template system.
12. Developer tools
Finally, an add-on of sorts that Apple bundles itself. Access the Advanced section of Safari's preferences and check 'Show Develop menu in menu bar'.
This menu provides access to Apple's surprisingly comprehensive range of tools for designers, enabling you to spoof various browser user agent settings, inspect the code of the current website, and disable page components.