Hey, for those of you who have yet to buy the MHL cable, I got a link to a coupon from the xda forums for 50% off at t-mobile stores. You can get the cable there.
Coupon link:
http://blog.t-mobile.com/wp-content/...Example-9b.pdf
I'm not sure if the coupon HAS to be in-store, but here is a link to an adapter (won't allow charging at the same time like the one available from Sprint, linked earlier in this thread, will)
https://www.t-mobile.com/shop/AddOns...rue&catCode=23
xda forum link (OP has several links, including the coupon, regarding the MHL cable/adapter):
MHL Adapters - xda-developers