Log Cabin Sporting Goods in Craig is the largest & best stocked fishing equip store on POW, # is 907-826-2205. Pretty friendly group, willing to give out good info.
There is a fly shop here in Ketchikan, in the Sockeye Sam's building (907-225-3260), owner is pretty familiar with POW. Also Tongass Trading, 225-5101, but keep your wallet open in Tongass Trading.
Are you flying up or coming on the ferry? If you send me a PM with your address, I'l mail you a copy of the AK Dept of Fish & Game sportfishing brochure for POW, it has some pretty good info on run timing, etc. I think I have an extra copy of the Forest Service map too.
I live in Ketchikan but work a lot over on POW. If you fill me in on what you are considering (flying up or taking the ferry from Bellingham or Prince Rupert, chartering, float plane fly-outs, camping, lodges, bringing a boat or renting one) I could fill you in on what I've experienced. Here's a couple other web sites:
www.adfg.state.ak.us/
www.princeofwalescoc.org/
www.ketchikanchamber.com
Hope this helps, like I said if you shoot me some specific questions I'd be glad to pass on what I know.
Dan