For your 40D, check out the Tokina ATX 12-24 Pro DX zoom that i mentioned above. It gets really good reviews, and if you look at the thread on POTN you can see the results for yourself. I'm not really into macro, but on POTN I'm sure you'll find lots of good advice and info.

Don't forget you can convert many lenses into macro lenses by adding extension tubes. Actually, now I come to think of it I'd love some extension tubes for my 5D (with 100-400L and 24-105L, as well as the nifty fifty).

If you see any special offers on the Canon 16-35 II I would be SERIOUSLY interested. The widest I can use on a FF camera is about 16 and that lens is supposed to be absolutely superb. I currently don't have anything wider than 24. In fact, a Mk1 at a good price would be very attractive as well.