Not sure if this is considered as advertising... but I've already done this five times and want to share the wealth.
So, essentially, you text "power" to 24477 (spells out CHIPS... it's a Doritos promo), you'll be given a code to redeem, and you cash it in on your 360 for 100 MS points. You can do it once per phone, so you can bug your friends, relatives and in-laws for codes.
As aforementioned, I've done this several times already, and there are several sites you could find on Google where others say it's legitimate if you don't trust me, and only regular texting fees apply (ie, you won't be getting a random charge come end of the month), the only downturn is that it subscribes you to a Doritos texting list, but you immediately reply with "stop" and be free of them.
It doesn't get much better than free MS points, so godspeed, my fellow Charterz. XD
(PS. Sonic 2 is only 240 points for a limited time, I'd take advantage of that :P)
Brawl FC: 0473 - 7465 - 0612