The American Institute for Conservation of Art and Historic Works (hence forth the AIC) has an interesting wiki of a pretty technical basis that I just stumbled across. It's not pretty or fancy but you can get in touch with your inner artist geek reading about varnish, stretchers, paper resizing, mountmaking(!), and other arcane and not so arcane topics.
What led me to it was research on varnishing. Whew!
Like other wikis, there is a wealth of information and huge gaps in areas where no one has actually stepped up to write an article someone else recognized as useful enough to generate a placeholder page. Since the target is conservators, most of what I've looked at was rather dry and technical, but extremely informative.
Got some time to kill? Check it out at: http://www.conservation-wiki.com/wiki/Main_Page.