The i-knead is the mosted bested thing I have found (actually give by yellow) to deal with calf knots. I can sit on the floor and rest/move my leg on it while I respond to email or watch a movie. So much better than a ball or stick.

http://www.trisports.com/i-knead.html

For a very effective but initially more painful release, kneel on your hands and one knee while using the other knee to knead the other calf.