Predatory Plants appears to be reputable. I'm adding them to my list but have never ordered from them. They do have a facebook page and almost 1200 fans.
Other stores that I would personally recommend are as follow (I've bought from or traded with all these stores at some point or another):
Cook's Carnivores:
http://www.flytraps.com/scripts/prodLis ... ategory=17
California Carnivores:
http://www.californiacarnivores.com
Conner's Carnivores:
http://www.connerscarnivores.com/store.html
Exotic Plants Plus:
http://www.exoticplantsplus.com/orderform.htm
Flytrap Shop (run by Andy/adnedarn, owner of TerraForums):
http://www.flytrapshop.com/servlet/the- ... Categories
Cascade Carnivores:
http://www.cascadecarnivores.com/
Equilibrio Carnivorous Plants:
http://www.equilibriocarnivorousplants.com/
Sarracenia Northwest (look at the "Plants for Sale" block on the far right):
http://cobraplant.com/
Meadowview Biological Research Station's order catalog (specializes in drosera):
http://www.pitcherplant.org/Online-Catalog/index.html
Wistuba (EU, site under construction, no sales atm):
http://www.wistuba.com/shop/
Buyer Beware:
http://www.blackjungleterrariumsupply.com/
Black Jungle's plant quality has become questionable in recent years; I've seen pics of people receiving half-dead and etiolated plants from them on numerous occasions. The one plant I ever ordered from them was fine.