EF24-105 + extension tube = nice macro lens
It certainly is! I always carry a 12mm extension tube with my 24-105 which gives me just enough up-close ability for light macro work.
This series was taken with that combo on a 30D - handheld and manual focus, as the subjects were bobbing around like mad and I wanted to wait for them to hit the focal plane. All a bit hit and miss, but I got some keepers.