Gamestop has discounts on MS cards, but you have to buy a console to get the deal.
The only other deal I know of is a 3 month Live card that is half off, but I can't recall which retailer has it advertised.
Maybe Amazon will have a deal on them at some point during BF/Cyber Monday or before X-Mas (I hope).
Other then that, unless someone knows something that I don't, BF is looking pretty stale for MS points or PS Plus cards etc.
Check the video game deals forum on here and there are two threads that should be right by the top of the page that are full of Black Friday deals and all.
Sorry I wasn't of more help but good luck.