Verizon definitely does. When we signed up for it we just had to provide them with my husband's military email address to verify his military status. I think we save 15%/month on our bill as well as 20% on all equipment.
ATT gives it, I think its 19% all you need is a FAN # - call ATT Business and provide certain info, they may email or send you link to a form to fill out by the soldier and if I recall, by the commander or unit and then once faxed or sent in, they assign you the Army FAN#. I did this years ago. I actually work for Citigoup and their discount is higher so I have not used it anymore, but I know it still should work.
My husband and myself just renewed our contract and asked about any military discounts. The gentlemen informed me that once you have a military e-mail you simply have to e-mail them from your military account all your info (account #, etc), and you will receive a 15% discount off your monthly bill.
AT&T just charged me a Sponsorship fee to get my military discount. BEWARE! This fee was $36.00 and my discount was $12.00. What a deal! I haven't had the chance to ream them out yet but they didn't mention the fee when I let them copy my ID for the discount.
I just signed up for this "Individual Responsibility User" plan for both mine and my wife's iPhones and the initial fee is high, but the discount is for the rest of our service agreement and thus worth it.
All the Soldiers I know who have iPhones (90% hah) are taking part in this discount program. Not sure what our discount amount is yet, but I think I remember hearing it was 20%.
I'm guessing troll (on 20828816)--"You ain't gotta be head cashier at Wal Mart" to know a monthly discount adds up.