We have a Penzey's spice store in the area, and occasionally we stock up on various stuff there. The Man and the girls were going out there, so I asked him to see if they had minced ginger.
He brought home powdered ginger, which we already had. He returned it and came home with crystallized ginger. Tasty, but not what I needed.
Finally, I ended up buying it myself--you can get it at many supermarkets in the part of the produce area where they also sell bottled garlic. I also get it in Asian and other ethnic supermarkets.
Powdered ginger is fine for baking, but for the Asian style dishes I make like Sweet and Sour Chicken and Crockpot Pork Ribs, its flavor gets lost in the cooking. Minced ginger is as close to fresh as you can get without grating and mincing a ginger root--and I don't use ginger often enough to keep it in my produce bin. This kind lasts indefinitely in the fridge.