Skype is a program you can download to your computer for free. Once on your computer, you can use Skype to make calls to other people who have Skype on their computers. These calls are completely free. To make it even better, if both of you have a webcam, you can make video calls so you can see each other. If that's not enough for you, you can pay a monthly fee and call home and cell phones. There are cheaper ways of doing those though.
Its a great service. It's perfect for military on deployment or kids away at college. We try to talk on there once a week. It's tough with the time difference, and our schedules. When it is good for both of our schedules, my roommate is usually sleeping, so we end up not doing it, or I resort to whispering. So we have only been able to do it a handful of times. The other problem has been that terrible Internet connection out here. It has gotten much better though. Below are a few pictures I snapped while talking to her. She will most likely be angry, so I'm sorry. I just couldn't resist. At least I didn't post them on your facebook ;)

Martini and Christina

Roo and Christina

Not sure what I said to get this reaction. If you have a good guess, please post in the comments.