defaults write com.apple.Safari WebKitInitialTimedLayoutDelay 0.1
defaults write com.apple.Safari WebKitResourceTimedLayoutDelay 0.1

Useful, without AdBlock, to delete HTML elements such as banners and similar spam. This works for CSS too and is thus an excellent way to get rid of spam CSS curtains.

The only drawback is that the changes you make to webpages do not persist across refreshes.

Safari from version 5.0.1 onward uses DNS prefetching. This feature can be turned off by issuing:

defaults write com.apple.safari WebKitDNSPrefetchingEnabled -boolean false

in a Terminal.

These extensions seem to be working (and integrating well in Safari 8) and are not bugged:

• Adblock Plus, by Eyeo GmbG, to not be confused with the other one.
• Ghostery for blocking trackers.
• 1Password to store passwords.
• QuickNuke to remove annoying HTML elements.
• Videobox to download video files.
• Page Rank to check the Google page rank on pages.