This is the official site of the creators of Blades of Exile. Here you can download the old demo version along with some new scenarios and stuff. The BoE scenario list here though has not been updated for a long time though.
Spiderweb Software Forums
This is the official forum for Spiderweb Software and their games. You can join and discuss anything about them here. The Comprehensive Scenario Rankings are here too, where you can review scenarios for BoE and BoA after you play them.
OpenExile By Chokboys
This is where you can download the open source full version of Blades of Exile. If you still haven't played BoE yet, get going and download it.
Truesite for Blades
This site is a godsend! It contains walkthroughs for almost every BoE or BoA scenario out there, plus other useful things like maps. You can also download new scenarios here. It is also home of Pixle Profusion, which is the best BoE Custom Graphics archive out there in my opinion. The site is maintained by Jewels.
Brett Bixler has several sites he maintains for Blades of Exile and Blades of Avernum.
Brett Bixlers Page
This is Brett Bixler's page on Blades of Exile. Includes his scenarios and walkthroughs, as well as his own graphics archive.
A searchable Blades of Exile scenario archive.
This is Brett Bixler's Blades of Avernum page. It has an extensive tutorial on making BoA graphics as well as a searchable graphics archive.
Brett Bixler's Louvre inspired me to do something similar for Blades of Exile.
S.M Adventurer's Blades of Exile Page
A new site for Blades of Exile.