Congrats Matt.
The Canon 40D is the best APS-C (crop) size camera to come out of Canon yet IMHO !
As for a workhorse lens, I highly recommend the 24-105mm L as a top all-rounder and that's coming from someone who has tried and owns a few lenses.
Later you can get others as your needs arise.
BTW unlike previously posted advice, there's some very nice EF-S lenses, even for astro !