Others have given more sophisticated advice, but let me mention the most basic technique: use longer exposure times by using a tripod, including perhaps a mini-tripod or bean bag for low level nature close-ups. (I hate flash, so failing this, would go with reflectors.)
Another idea is "in-camera stabilization", either in-lens or in-body sensor based, but for now Canon has no such option for macro lenses. But since every other DSLR maker now offers in-camera stabilization of macro lenses (Nikon 105/2.8 VR macro lens, in-body stabilization from Sony, Pentax and Olympus), I imagine that there will soon enough be either a Canon IS macro lens or Canon DSLR's with in-body stabilization.