I seconnd the M&Ms, I know from experience they don't melt, and by coincidence, a 'any soldier' coordinator wrote that just the other day. I have to get back into sending packages. I was sponsoring a Marine who came home, and I haven't been sending since. I'm currently recovering from a hospitalization and have been doing letters and cards to Sailors via. any soldier.com.
Don't forget to send gum, jolly ranchers, and other hard candies. It's dry in the desert.