Mark --

Certainly the 7-ton pier thread on this very forum was one of my favorites.

Doc G has a nice page on design considerations (including a very good dome vs. roll-off-roof discussion):

http://www.mapug-astronomy.net/ragreiner/ObsDesIndex.html

The MAPUG archive has good info on both observatories and piers:

http://www.mapug-astronomy.net/AstroDesigns/MAPUG/Obsrvtorys.htm
http://www.mapug-astronomy.net/AstroDesigns/MAPUG/PermanentPiers/PermantPier.htm

Of course, there's also Bill Arnett's list (which must be the most complete list of amateur observatories in existence):

http://obs.nineplanets.org/obs/obslist.html

Bill Arnett's "Japanese tea house" was quite an inspiration to me. This one might be subtitled "Just how good an observatory can look":

http://obs.nineplanets.org/obs/obs.html

For those in colder climates, this one is a must read:

http://www.microprojects.ca/Observatory/Observatory.html

These last two might not be as generally applicable, but they were the closest to what I wanted to build and so very helpful for me:

http://starkey.ws/new_observatory.htm
http://www.arksky.org/ASO_PJ.htm

-- Jeff