Thanks, Marty. And thanks to Roman for sharing his tutorial.

Here's how to do the click-to-expand thumbnail:
1. From within your photo hosting site create and copy the link to your picture.
2. Keep this dummy sequence handy somewhere in your computer:
[ URL=yourlinkhere ][ IMG]yourlinkhere[/IMG ][/URL] Note I had to insert a few spaces in the dummy link to make it show as text instead of a picture place holder. Leave the spaces out)
3. Paste the dummy sequence into your post, then replace the first 'yourlinkhere' (http through .jpg) with your picture link.
4. Then replace the second 'yourlinkhere' in the sequence with your link.
5. Now replace the "orig" (or whatever the size designation) in the second link with "thumbnail" and Voila!

If that's confusing let me know.