The one at DTD is completely random, they don't announce times. I have yet to catch it when it's open.
Mouse Gears has a very large board and when I was there in May, they had it out at 1 pm each day. The pin kiosk in the middle of Future World also has a small board and I have seen it out at all times of the day. Neither location will get the board out if you ask.
The pin store in Fronterland in MK has a pin hat. It's basically a felt cowboy hat that has pins in it. It's very small and does not have a lot of pins. If a CM is not carrying it around, it's usually hanging behind one of the registers. I've asked nicely in the past and the CM at the register has gotten it down for me. I've also seen a pin washboard and a pin Duffy at that store but not on my resent trip.
As for AK, I've seen boards at a few different places including the Gardens Kiosk on Discovery Island but the best one is the safari pin vest that they have in the store outside the gates on the way to the buses. They will get it out for you if you ask.
In HS they also have a pin board at the pin store under the hat. No idea when they get it out though, I've only run into it one time and they won't get it out if asked.
Don't forget also that all of the resorts have boards either in the gift shop or at the concierge desk. All you have to do is ask and they will get them out for you. One of the best ones I've seen is at the Meadows Trading Post in Fort Wilderness. The board there is huge and had some really nice pins on it.
