I just wanted to bring to your attention the...Buddhist Cultural Centre's Bookshophttp://www.buddhistcc.net/bookshop/
I found this link originally on the Links page of Access To Insight.
I ordered a stack of books from them recently, and found their prices to be really good (even if the postage rates are only so so).
They also have a very diverse and extensive range of books, many I'd never even heard of before. Just be careful when ordering to ensure that you order the books with the EN (English) label... unless you enjoy reading Sinhalese of course.
The prices are in $US, so if your local currency is faring well in comparison to the $US, it might be a good time to invest in some Dhamma Books!
Feel free also to share links to other good sources of Dhamma Books!