I usually only buy ASA-specific items through the ASA store. I've found that a number of other sites have equal or better items for better prices and usually faster service. Tom mentioned Lester's and Honig's - both of these provide excellent products and service and their prices are pretty good too. I'd recommend both of them to anyone. I'll add Mike Shields' store -
http://pennsylvania.purchaseofficials.com/home.php
to that list. Mike is very fast with his deliveries, good on pricing, and very good on quality. If you do high school sports in Pennsylvania, you already know that.