Focus Stacking - options (Mac) (1 Viewer)

I currently use a Canon 100mm 2.8L Macro lens primarily for subjects such as Butterflies and small Insects in the field.
However I find DOF is always an issue and often it is difficult to get all the subject in focus (even using flash ).
I have read about 'Focus stacking' and have wondered if this technique may help in some circumstances.
As I am not sure how effective this might be (especially in the field ) I am ideally looking for a Freeware program I can at least try which is compatible for a Mac.
I have also seen it mentioned that Photoshop has something similar but if so I am not aware of it or how to access it.
I have Photoshop CS5.1 myself so if this can be used I would appreciate any feedback concerning how to use it or how effective it actually is.
I fully understand how Focus stacking can work for static subjects but is it practical for subjects such as live insects which more often or not are not static for long.
Any feedback or recommendations concerning a suitable freeware program (for Mac) much appreciated.

Thanks

I've seen some good examples of focus stacking done in the field (Nikolas Rahme for example), but that's not easy. Mostly it is used on extreme close-ups way beyond 1:1 magnification. Other frequent usage is to capture whole object in focus (similar effect as it had been taken with small aperture, eg. f16) but having nice bokeh background in the same time (like it has been taken with aperture wide open @ f2.8 or similar). The second situation can be also achieved without focus stacking though - the background simply has to be far enough from the object.
Most of the opportunities for focus stacking are on early, cold-ish (for insects to be inactive), windless mornings - which are rare (at least from my experience). You also need a focusing rail of some sort on a tripod.

I think the program used most frequently is Helicon Focus - If I'm not mistaken, it has 30day free trial. Available also for Mac.

But I myself have come to conclusion that it's a bit too big of a hassle to really get in to it. And I have found that I can get enough of DOF in most of situations - especially on butterflies and similar sized insects. Maybe you can give some examples of pictures where you think depth of the field is lacking?

Hi,
I've tried Zerene Stacker (not freeware, but available for Mac and with 30 day free trial) which seems to do a brilliant job of "glueing together" the stepped phots. The biggest problem is getting beasties to stay still long enough to complete the stepped sequence. You do need a static subject and rigid camera support.

There is a photoshop Cs5 tutorial here http://www.youtube.com/watch?v=intzev1gsbI looks really simple to do.