The March 809 is the brewer standard but there are other pumps out there. I just picked up a Laing 1212-sm-26-st which is basically i super high end stainless version of the march pump for $70 on Ebay. most of the Laing pumps would work well and are much cheaper. In addition, Teel pumps are nice and have the same advantage (no homebrewer competition).
You want a magnetic drive pump (aka circulation, seal-less, centrifugal) with a head made of a material that can withstand boiling liquids without degrading. You want one that can pump at least 12 feet of head (maybe 8).
I like looking for industrial brands because you can find better deals. The pump I just picked up retails for $450, so $70 was a nice price.
Good luck on the search. Laing has a pretty good website for researching their pumps.
p.s. the old "best brewing" pump was the Teel 1P956 I saw one on Ebay a while ago and it went for $35, I was outbid at the last minute
Yeah, I have the march 809 and it's good but as previously stated it kind of takes some fiddling to figure out how to get it primed. Also, if there's a bunch of liquid on the "out" side putting back pressure on the pump it won't want to work. As I recommend in a different thread a couple minutes ago, do a water brew first once you get the pump installed to get everything figured out before it actually counts.