Adblock Edge, if you want to be a real stickler. It’s the same as Adblock Plus except it doesn’t include a whitelist for Google’s ads. Or you could just untick the “allow non-intrusive ads” checkbox in Adblock Plus. Whatever.
Google probably banned ad blockers from the Play Store as a way to combat the trend toward mobile devices that this article mentions. Part of me wonders how long it will be before they vanish from the Chrome Web Store as well.
Name another one that works as well for free.