Used Adblock Plus for many years. But it started to consume around 1.7 Gb of RAM per instance (Chrome profile when it's installed).
Got sick of restarting Adblock Plus and switched to uBlock Origin - same subscriptions, but much less RAM (not more than 300Mb for many opened tabs).

I found myself Adblock for Chrome. Very comfortably. Are there any plug-in for Safari?

If you want the first run page just go to chrome://adblockplus/content/ui/firstRun.html
This works in Firefox, I don't know if it will work in other browsers.

So I wrote fast and memory efficient domain blocker which takes ca. 60 MB even with tens of tabs in multiple windows: Domain Blocker

Adblock plus has quite extensive database of various filters which is great and hard to beat but I chose different approach - build custom list of domains to block. This way you're active participant of the ad blocking process and it's fun and insane at the same time to discover how many 3rd party services average website uses.

It's more suited for power users who like to have things under their control.

[Edited by petasittek, November 11]

Blocks most, if not all, advertisement.

Though Adblock Plus for Chrome can block most Youtube video ads, it doesn't do a very good job blocking these sorts of ads on other video websites. And just for clarification, when I say "video ads", I'm either referring to the videos ads that play before the main video itself, or to the little banner ads that pop up within the main video while it's playing.

Adblock Plus for Firefox is still king when it comes to blocking video ads in general. If you're watching a video on (for example) Engadget, Adblock Plus on Firefox will block both the ads that play before the main video itself, and the small banner ads that pop up within the main video while it's playing. Neat.

However, on the Chrome version of Adblock Plus, these ads remain (sadly) unblocked. Adblock for Chrome, the main alternative to the Chrome version of Adblock Plus, also has these flaws with video-blocking. In this regard, neither of these two major Chrome adblockers do a very good job. For now, no matter which adblocker you're using on Google Chrome, you're still going to have to watch video ads. Shoot. :P

Adblock Plus: after FF4-installation ABP first was not compatible to Firefox 4
Without AdblockPlus It's hard to surf internet.
Solution: In the Addons tab, right-click AdblockPlus and use Find Update.

This is really the most useful addon ever.

@em4020: Xmarks is useful too, but in my opinion, nothing beats not seeing ads (is that a double negative?).

In the meantime I have added UnMHT to http://alternativeto.net/desktop/unmht/
I think, it is so important for daily use, that it shuold be found on http://alternativeto.net .
I agree with Xeogin, that Tab Mix Plus is also a very useful Firefox add-on:
https://addons.mozilla.org/en-US/firefox/addon/1122

"Adblock Plus" belongs to the 4 most necessary Firefox add-ons for daily use:
Xmarks (1), Adblock Plus (2), Add To Search Bar (3) and UnMHT (4).
(1) http://alternativeto.net/desktop/xmarks/
(2) http://alternativeto.net/desktop/adblock-plus/
(3) http://alternativeto.net/desktop/add-to-search-bar/
(4) https://addons.mozilla.org/en-US/firefox/addon/8051

The internet would fail without this add-in, it blocks ANYTHING. It's one of the few things that NEED to be open source, cause if not, companies could buy-out advertising space, like almost any other ad-blocker.