I'm finding it harder to figure out where to post this tidbit than to solve the original problem. But, I felt too guilty seeing 38 pages of search results for "center logo". Anyway, I was finally able to center my logo in my Zen sub-theme by adding "float: none" and "text-align: center" to the #logo part of my renamed css.
I'd post it somewhere else, but I have no idea if this works for Garland sub-themes etc, and I also don't know if its the "right" way to do it. Thanks again, Zen is awesome.