What are the most notable attacks on pools?
Exploits / Hacks resulting in BTC theft:


The Linode Incident - 46,000 BTC were stolen due to the compromise of a single employee workstation.
Slush's Backup Hacked - 3094 BTC stolen after a backup of Slush's pool was compromised.
Mt.Gox Database Theft - a reported 100,000 BTC were stolen, and another 400,000 BTC reported 'missing'. Mt.Gox shuts down and stops honoring trades of compromised coins.


[D]DoS Attacks ([Distributed] Denial of Service):


Slush's Mining Pool DDoS - A DDoS attack which lasted nearly 2 days before being recovered from.


This is a CW entry in the hopes of creating a clean index of info about all known (and notable) attacks against mining pools. Please maintain it as new information becomes available.