Since we are talking about district tartans here, I thought I'd give a little plug for my Compendium of District Tartans_.
http://albanach.org/cdt.htm

It's the definitive collection of district tartans from all over the world (over 450 of them), including pictures, thread counts, and history for each one.

Also, my web site, District-Tartans.com.
http://www.district-tartans.com/

Here you'll see pictures of many (not all) of the tartans in the CDT, though no thread counts or history (just a designer's name and date, if known). But you can purchase items from this site.

I just got my first district tartan kilt, in the Mull tartan!
Aye,
Matt