I'm in the same boat. Just bought a 100 2.8L IS Macro last week. Played around with it over the weekend photographing flowers and just getting an idea of what I could do with the lens. I've seen the same books mentioned but haven't purchased anything.
My nephew took a workshop with Mike Moats (tiny landscapes: http://www.mikemoatsblog.com
) but Mike only conducts his workshops in the Midwest and Southeast. So, if you live in that part of the country, you might want to check out his macro workshops. There are others that give workshops, but Mike Moats doesn't charge you an arm and a leg.
I'll probably checkout the usual book suspects.
BTW - Mike Moats has an eBook: "Creating Art With Macro" that's $14.95