There's a few things to look for when shopping for router bits; carbide thickness, ground quality on the carbide, quality of the brazing, etc. Also reputation is a good thing to follow too. I stick with whiteside because they are the best router bits made. Fine woodworking just did another test on a bunch of manufacturers and whiteside came out on top again (they were tested back in 1993 too with the same results). With free shipping, holbren has the best prices bar none on whiteside bits.
Other good quality bits include Bosch, Freud and CMT, but those you'll not find at whiteside prices often.
