Hybrid IS. It also corrects shift shake in addition to rotational shake.
+1 on the 100mm f/2.8L Macro IS. It's a versatile lens, good for portraits (f/2.8 will give you more OOF blur than your 24-105mm), and also good for handheld macro shots. Examples (handheld):
EOS 7D, EF 100mm f/2.8L Macro IS USM, 1/160 s, f/11, ISO 640
EOS 7D, EF 100mm f/2.8L Macro IS USM, 1/150 s, f/13, ISO 100
Great shot of the hopper Mr. Neuro. AF or MF... Do you use macro rails?
40D is crop... so you need a UWA lens too. The 24mm is closer to 40mm on crop, thats not wide enough for some situations. 15mm on crop = 24mm on FF.
the 2 lenses you have are great value and range. Consider substituting the 17-55mm instead of the 24-105mm (which is better for FF due to the range).