I've just read some nice tips and discount codes and it occurred to me that a dedicated thread might be a good idea. Thanks to Frederick McGuire and Bob Loblaw for their posts.
I'll start by pasting the GC code:
Because we love you we want you to save some coin on your next purchase with us. Looking for a new pipe? Here is a 15% off coupon code good for anything in the store. This code expires 07/09/2012. Coupon Code: NWCP12