Mark K's testing page. A great resource with tons of data and useful info.
John's Audio projects page. Again, plenty of driver info and diy kits.
Siegfried Linkwitz's homepage. The original, and still one of the best diy audio sites out there.
Another great loudspeaker test and review site.
The old Usher audio North American distributor website. Has some great speaker reviews here.
A great compilation of diy projects: