I am building a power supply and it will be housed in a plastic case with a fan. I understand the wisdom of grounding a metal case, but in my case (no pun intended) I have an aluminum front panel. Should I ground it? My feeling is yes, but I want to know if this is correct as I haven't seen metal front panels grounded before.
It depends on the type of power supply and how many of layers of insulation you have on high voltage lines.
Is this an AC to DC power supply or do you have mains coming into the box for any reason?
If you have a mains (120 or 220 VAC) live line (or other hazardous voltage - depends on application but generally above 60VDC) in the box and it is theoretically possible for a fault to result in a loose live wire that could reach and come in contact with the aluminum panel, it must be grounded (and with a solid connection that is capable of passing relevant regulatory ground-bond testing requirements).
Without this, a fault could lead to the panel (and therefor human operators) being exposed to live voltage. With it, it will result in a short to earth ground that will blow a fuse / pop a circuit breaker.
Ordinarily, the answer would be yes, and it can't hurt. However, since the rest of the case is plastic, grounding one side out of 6 is not going to give much benefit. Unless, of course, you're going to do something good like sputtering a metallic coating on the inside of the plastic and grounding that.