I'll second that kryptonite lock. As for bike security my personal tips?

No quick releases. Either locking skewers or just plain old hex bolts everywhere. Idealy in such a manner to be a real pain in the ass to remove quickly.

If it's a commuter bike that's going to be locked up make it UGLY. Make sure to keep that frame paint pristine under your cable runs. . . by wrapping it in duct tape. . if you do get a major scratch by all means patch it . . with the wrong color paint and poorly. Any fancy looking equipment should have the logos removed. Add a few walmart smile face stickers for color. Be sure that nothing about the bike says "sane people would ride me or pay money for me".

If you're going to be away for a LONG period of time get a second lock of a different kind (if one is chain the other should be cable or a U lock, etc). Basically make it really awkward to steal.

Oh and it always helps to park it on the same rack as a really nice looking bike with a crappy lock.