Thank you to a friend who alerted me to this:
Text the word XBOX to 24477 and get a free 48 hour trial code for XBOX Live Gold.
Terms, Conditions and Instructions: www.xbox.com/LIVE/trialcard48 
Standard text messaging rates apply.
This free 48 hour trial code is sponsored by Doritos and the number “24477” belongs to them. I texted XBOX to the number and instantly I got a message back saying:
Here is your code for a free 48 hour XBOX Live Gold Trial XXXXX-XXXXX-XXXXX-XXXXX-XXXXX-XXXXX courtesy of Doritos!
I do not know how long this promotion will last, so grab it while you can. If you already have Xbox Live Gold, you will not be able to extend your membership by 48 hours, but you can save this code for when your membership expires. You should also be able to get multiple codes if you use different phones seeing as Microsoft does not limit how many trials you can run on your account (as far as I know).
Source: SlickDeals.net