http://www.disneynow.com/profile/web/index.cfm?PKwebID=0x37065136&varPage=home is a direct link to the list. When my travel buddy got a list from City Hall, it was not as updated as this one, so you might just want to print this one out in advance.
Pressed coins are one of my favorite things! If you press one on a wooden sidewalk/porch in Frontierland, though, make sure you put your hand out to catch the penny. It may fly right out of the holding area...as mine did! I looked down and there were probably 30+ pressed pennies (including mine!) fallen in-between the cracks and inaccessible.
Machines can also go down (sometimes for a long time, or sometimes just for the day). I was super-excited to get the WALL-E set in June and got them as soon as I could! One night when I went to the arcade, though, the machine was out of order.

It was fixed the next day, but if your heart is set on a coin, I suggest you don't wait until the last minute.
I think nickels are 80 cents but I'm not certain. Nickels are awesome, though, because they don't tarnish! I don't remember how much the dimes were; no more than $1.10 total, but it might've been 85 cents.