I don't know anything about Visual Mill, but there are various levels of nesting programs available. The simplest is a rectangular nester. The programs takes the largest rectangle that your part will fit in and tries to nest that. If you have odd shape parts that isn't too good, but works well for cabinetry panels and such.
A true shape nesting program is more versatile, but more expensive.
From my experience, you can next manually better than any CAM solution. That is if you have static nests. Meaning that you just want the best nest for a set quantity and variety of parts. I just load the parts in my CAD and move them around until I like the fit.
If your parts are always different and every day the quantities change, then an automated nesting program is applicable.
http://www.mtc-limited.com/turbonest.html http://www.merrymech.com/nestmast.htm