Boy, that's a wide-ranging question. I'm guessing your friends will be hoping to fish while they're up here. Here's what I recommend to all my family and friends with the same sort of plans:
First, buy a current copy of "THE MILEPOST." This is a travel guide to Alaska that's about the size and thickness of the annual Cabela's catalogue. It gives specific, detailed information on just about every location in the state that you can get to by driving. I buy a new one every year just to find out which motels and restaurants have opened or closed and which roads have washouts or repair projects in the works. http://milepost.com/
Next, not knowing just when in the summer your friends are going to be here, I suggest they get a copy of the run-times for salmon and best catching periods for other fish. http://www.outdoorsdirectory.com/runtime.htm
Heck, a big part of a trip like this is the fun you have when you're planning it.
And, for sure, contact a local expert, like Hap, to get the inside information you just can't get from travel guides or tackle stores.