For me, it's a Kensington lock. I have a new one with a combo code instead of a key (one less thing to lose).

Most notebooks these days have a security slot that the lock fits into. In most Marriotts, you can find a hole in furniture, a leg of a table that is cross braced, or even a similar chair leg to wrap the cable around/through.

NOTHING will deter a determined thief, but a cable lock keeps honest people honest.

$30 or so at the usual suspect electronics or office supply stores.