Did someone say Baxter?
I make 6 or 7 trips to Baxter each season climbing and hiking, and writing for the ALDHA Companion.
Some quick thoughts:
Check out
http://www.baxterstateparkauthority.com/index.html to learn about reservations, see campground maps, read rules, and find out about the rolling reservation system - where held back sites for Mainers go up for grabs two weeks out.
Only go in June if you like blackflies. Mid-August to mid-September can be glorious.
You're probably not going to get a cabin, those are prized 'gets' and go to Mainers who play the system.
Chimney Pond might be my favorite campground on Earth - but it doesn't open until June 1st, when the blackflies invade.
If your goal is only Katahdin's Baxter Peak, stay at Abol Campground two nights. The Slide looks tougher than it is.
Roaring Brook is a 'touristy' campground - ask for the quieter walk-in sites, and start all hikes before the gatehouse opens.
Katahdin Stream can get busy, but it's a fantastic base camp. I advise southbound thru- hikers to get a lean-to here for the nights before and after their climb.
Nesowadnehunk (say SAW-dah-hunk) has group sites, way up the perimeter road from Katahdin Stream, is good for hikes of Doubletop, Fort, Coe, etc.
Foster Field on the west, and the brandy new Bear Brook on the east are group sites. Bear Brook has both bears and a brook, and is wicked nice as an alternative to Roaring Brook.
Loop hikes out of Sandy Stream or Chimney Pond can 'bag' peaks galore. Hamlin is my favorite side of Katahdin so keep it our secret, please.
The Wilderness Map Co has a great map of Katahdin, DeLorme has a great map of the whole Park.
Please do other stuff besides climbing stuff. There are moosey ponds, canoes and kayaks, natural water slides, flat backcountry hikes, and good fishing.
The Great Basin from this October:
http://www.whiteblaze.net/forum/vbg/showimage.php?i=28768&catid=member&imageuser=314
Chimney Pond from this September:
http://www.whiteblaze.net/forum/vbg/showimage.php?i=27989&catid=member&imageuser=314
Katahdin from the east this past June:
http://www.whiteblaze.net/forum/vbg/showimage.php?i=25587&catid=member&imageuser=314
Enjoy planning your trip!