[TomGuy]

Adblock Plus

http://adblockplus.org/en/firefox

[steve86]

That, too. First one I install! Just the other night noted that several pages would not even finish loading on an old memory-constrained laptop without Adblock installed. Noscript also saved a chunk of memory.

[Carriage Hill]

Also works on Opera:

http://adblockplus.org/en/opera

[rarestia]

Agree on AdBlock Plus. It’s a must have. Also check out their pop-up blocker which is amazing for many foreign news sites.