With free program CombineZM, you can use to make photos with an "infinite" depth of field.
Whenever enough people start experimenting with a new photo technique, it invariably gets its own name. In this case, it's become known as "focus stacking." The name makes sense because you use a series of three or four photos, each with a slightly different focal point, so a different part of the picture is sharp in each shot. You use CombineMZ to "stack" the photos and combine them so all the in-focus bits are merged into one photo that is sharp from front to back. Pretty neat, right?
After you're done shooting, copy the photos to your PC and start CombineZM. In CombineZM, choose File, New and select the photos you just shot. You should see one of them appear in the CombineZM window.
From here, it's all automated. Choose Macro, Do Stack. Then sit back for about 5 minutes and wait while the program combines the photos into a finished product. I've gotten pretty good results, especially when I'm careful to keep each photo in my series aligned by using a tripod. If you get a lot of blur or artifacts in your focus stacked shots, you might need to tweak the program a bit--check out the included help file for details.
CombineZM has one more trick up its sleeves: You can use it to make a movie out of all the frames in your focus stack. Choose Movie, Make and the program will use each frame in your sequence into a movie, so you can watch the focus ripple from one end of the scene to the other--sort of like the way the focal point will change from one subject to another in a film or TV show.