I was trying Omniweb the other day on a very standard page (from the Emacs lisp tutorial by Xah Lee at http://www.ergoemacs.org/emacs/elisp.html) and I was shocked to see adverts in a box on the right side of the screen.
Safari and its extensions had got me used to a web without adverts invasions, without irrelevant contents, and with much less energy use when I'm unhooked.
I guess other browsers have similar features but after a bit of hesitation, I quit Omniweb and reverted to Safari.
The extensions I use are the following:
Adblock blocks ads on all websites.
Adblock Plus seems to block even more stuff
Directlinks makes indirect links on Google and Facebook direct
Ghostery stops tracking engines and shows you which were going to track you
StartPage HTTPS enables the StartPage search engine, through HTTPS
ClicktoFlash prevents Flash contents from loading automatically
ClicktoPlugin does the same for various plugins
Facebook Cleaner removes a lot of cruft from Facebook pages
Facebook improved improves on that experience
Clea.nr YouTube removes a lot of cruft on YouTube
That's pretty much it.
The site specific plugins are only icing on the experience since Adblock and Adblock Plus do most of the heavy work. Directlinks and Ghostery are important too, to keep sites from tracking you against your will.
Here is a good piece on ad blocking, via Daring Fireball:
"Welcome to the Block Party"