DISASTER-PREP TIP: How To Keep Your Cellphone Going As Long As Possible.
Note this in particular: “Text messages use a tiny fraction of the power required to make an actual phone call. In addition, there are very good selfish and selfless reasons to use SMS instead of calling during a wide-spread crisis: Texting helps keep the network from being overwhelmed, and texts are more likely to get through than voice calls.”
Also: “Need to check Twitter? Don’t forget that your 3G Kindle has a web browser in it.”