Adopt A Soldier - This 501(c)3 organization has been around a while. There are several other organizations which send care packages to our service personnel.
I wish it were as easy as during Desert Storm. Back then, we could send letters and packages addressed to "Any Soldier." We can't do that anymore for security/safety reasons. I wrote several letters each week and was surprised with all the guys who wrote back. I still have every one of those letters and cards and was fortunate to meet, in person, one of the soldiers I met through the mail.