Last year I bought an "Oriental mix" from White Flower Farms, and although they don't specialize in lilies, my bulbs were exceptionlly large, and what they deer did not eat bloomed beautifully that first year after planting (thanks to my Scarecrow Sprinkler my lilies are now protected from deer!).

This year, I ordered 14 different Orientals from B & D lilies, and the bulbs looked quite nice, but only two or three as big as what I received from White Flower last year.

Other places I will order from next year are:
The Lily Garden
Fogbelt Lilies
The Bulb Crate

There are also some nice Canadian suppliers (Liies in the Valley has a great selection), but I balk at paying the additional $15 certification fee (cert. that they are free of pests and disease). I'm sure others will have good suggestions as well. I haven't bought any lilies in stores in my area, but I'm sure the major home store chains such as Lowe's and Home Depot have a selection. My two fave local nurseries also have some, but not as good a selection as offered at online stores.

I've heard of an eBayer named "Buggycrazy" that usually has quality bulbs in the Fall, but recently read a post that she is winding down her lily business.