One of the most helpful sources was an article in the New York Times: Do it YOurself Eyeglass Shopping On the Internet. Before I found this, I noticed that many google hits were to online sales sites from the UK. The following are sites that seem at least interesting.
- Eyeglasses.com (now dysfunctional, but mentioned in the NYT article)
Essential link: GlassyEyes Blog. (Note later: This blog is amazing, with fine and useful comments. Great service to humanity.)
Now I have some fat to chew on.
Added Later: Here's another link: Eyeglass Liquidators . One post on the blog above mentioned they do trifocals, while others didn't.