In the event of a terrorist attack, natural, or man-made disaster, good communications can make the difference between coming through safely or not. During the aftermath of Hurricane Katrina radio operators were credited with saving many lives when people couldn't pick up the phone and call for help. There are several options available to you for emergency commo:
Obviousl, the first option is your land line telephone. Your plain old telephone may still work. If it does then it's the first thing to try. If not, then fall back to other methods of communication.
Charged cell phones along with car chargers, or your regular wall charger + a power inverter for the car. If you are in an area where they work, a cell phone can let you call relatives/friends outside the danger area. Phones with text messaging capabilities are more useful in emergencies than those without. Text messages require less bandwidth than voice and are therefore able to get through clogged circuits more easily, although the messages may be delayed in transit depending upon how saturated the network is.
FRS/GMRS radios. FRS doesn't require a license, while GMRS does (although it's just a fee, no test required, and the license covers your immediate family). Good for short range commo, e.g., between vehicles in a bug out situation. GMRS gives you somewhat longer range, though both require line of sight. FRS/GMRS radios can be picked up cheap at any of the big box stores, from Home Depot to WalMart, to Radio Shack. If you keep an eye out you may be able to find them DIRT CHEAP. E.g., I got a pair of Midland FRS/GMRS a couple years ago from MidwayUSA for the whopping sum of $6 + S&H.
CB radio. No license required. These are still useful, although you do hear a lot of garbage, much of which is not suitable for sensitive ears. I have a portable in my truck with an external magnet-mount whip antenna. It's great for listening to truckers for real-time traffic reports and has kept me out of several jams. Also good for short-range commo. Most CBs are AM, but Single Side Band CBs will give you longer range, although you'll only be able to talk to other SSB CB users.
Ham (Amateur) radio. Here's where it gets good, in my opinion. I got my ticket last year. Although you need a license, the entry-level Technician class license isn't hard to get, and the info you learn while studying for the exam can be useful. You can get a good handheld (AKA "handie talkie" or "HT") for as little as $100 which will allow you to transmit and receive on the 2M FM band. These are good for commo up to several miles if you have line of sight. I've been able to hit a 2M repeater ~10 miles away with my Yaesu VX-5RS using only 5W of power. I also have a Yaesu FT-7800R 2M/440MHz mobile radion that I'm in the process of installing an antenna on my house's roof for. With the roof mounted antenna and the 45W maximum output of the 7800R, I should be able to communicated with other radio operators for quite a ways. Since it's a mobile unit I can also pack it in a box with a 12V battery and a portable antenna, and take it with me.
Once I get my General Class license I'll be able to use the HF bands and transmit much longer distances without relying on a repeater.
I don't want to encourage unlicensed use, but in an emergency FCC rules about unlicensed transmission go out the window. You're allowed to use any means of communication to secure aid to preserve human life or property against immediate threats. IMO, the most important part about getting one's ham license is getting familiar with proper operating procedures, which are critical when TSHTF.
The resources I used to get my no-code Technician's licence were:
1. Now You're Talking! published by the American Radio Relay League.
2. "Amateur Radio No-Code Technician License Examination Study Guide and Workbook," by Bruce Spratling, W8BBS. (PDF document.) http://www.frrl.org/vetesting/2004%20technician%20study%20guide%20FRRL.pdf
3. The free online tests at QRZ.com.
Satellite phone is another option, although I have little knowledge of it.
A NOAA weather radio should be in your disaster kit, if one of your other radios doesn't also pick up these channels. In my case, both my Midland CB and ham radios already do, so I don't have a separate unit.
A portable AM/FM radio for listening to local news reports. If it picks up shortwave or the NOAA weather channels, it'll be more versatile. Some also allow you to listen to the audio portion of TV broadcasts.
Don't forget plenty of batteries, chargers, appropriate AC adapters, and a power inverter so you can plug them into the cigarrette lighter in your vehicle.