Bike Locks

Lock brands and where to buy-

f you can, use two locks of different type i.e. one U-lock and one chain, so that a thief has to carry two different tools (it's harder to carry both bolt-cutters and angle-grinder than just one).

A popular and trusted brand of U lock is Kryptonite. They have three strength standards for their U locks: Grey, Orange and Yellow. The Evolution Mini (Orange lock) is the preferred lock of couriers/messengers. It's small and lighter than the larger locks. The small size allows it to be filled, leaving little space for leverage attacks. Be sure to register your keys online: http://www.kryptonitelock.com/CustomerService/KeyRegistration.aspx  

Abus locks are also worth investigating. They tend to get good reviews and have better frame mounting options than Kryptonites. Granite-X Plus seems to be the standard. 

Thankfully things look better in Dublin than they do in Manhattan but this guy's video on bike security is informative and entertaining, even if he is a bit over the top:
http://www.streetfilms.org/hal-grades-your-bike-locking-3-the-final-warn...