Actually, I hate to contradict one as knowledgeable as Lynjo, but I feel I must butt in this time...
I used to use Shureline spinners. They
do work. However, if I am going to spin out a brush, I prefer a better-quality spinner, as the Shureline brand uses a brush clip that inevitably ends up crooked, causing a wild looping effect when attempting to spin out a brush... but the outer "sleeve" section of the clip seems to hold up fine. So the Shureline spinners are fine for spinning out covers, but IMO there are much better ones out there for spinning out brushes. My local Dunn Edwards sells a MUCH higher-quality spinner for only about $5-6 more than the Shureline goes for at the big box... I'm sure other dealers and brands are out there, if you seek them out.
In the end, a spinner is a spinner is a spinner - they all do the same thing... but some are definately manufactured using higher standards than others.
Oh, and GREAT tips above by BJ and Bauer! I love both ideas, the extended bucket and the "bunghole squeegee effect" are both entering my little black book of tips & tricks.