1.) AOL Instant Messenger: AIM or any other kind of instant messenger (yahoo, msn, etc.) is a great tool to download on your laptop or computer if haven't already. Something like this is particularly handy for study abroad students because of time differences, especially if you're looking for instant communication.
2.) Blog: Why not blog about your experience? You can send the link to all your friends and family, and update them on your life in a new country. As with this blog, you can do more than just use text-- try different forms of media. I'm sure everyone wants to see and hear about your new home away from home and your different adventures. Wordpress is another site for free blogging.
3.) International Pre-Paid Phone Card: If you use pre-paid phone cards as your main form of communication to call home, it is going to get rather expensive. Keep a couple around in case of emergencies, or if you go traveling for an extended period of time and need to touch base with your parents. You may need to call ahead of time (toll free number should be somewhere on the back of the card) to get a specific number to call from different countries and directions.
4.) E-mail: If you're like me, you're checking your e-mail constantly. Chances are, you're going to have internet in your dorm abroad, or at least at the university. You will probably get another school address from your host university that you may check more often, so remember to give everyone the new e-mail!
5.) Facebook: Like e-mail, it's something that I think almost everyone checks frequently throughout the day. Send a friend a message or write on their wall, and you'll get a response back pretty quick. Also, as I'm sure 99.9 percent of people know, it's a great way to share your pictures and links (if you decide to blog, this is a great place to put it).
6.) MySpace: Again, it's a similar concept to facebook except you can jazz it up with a more personal touch if you prefer.
7.) Skype: This was one of the best ways, in my opinion, to stay connected while you're abroad. It serves as a multi-purpose communication resource. It's part phone, part messenger, part web cam all in one. My favorite feature about it was that you could actually talk person to person with everyone and it's FREE! Also, international calls to landlines are super reasonable. As a side note: you may need to get a head set if you don't have one built-in to your laptop.
8.) Snail Mail: Who doesn't like to get a letter in the mail here and there? Or even a postcard. It's a nice change if you're looking to get away from technology. Just remember to look into the cost of postage, and how long it takes to get to wherever you're sending it to. Keep in mind it may take a while for them to receive it...I know I've gotten postcards from abroad and they've arrived after the person has already returned back home.
9.) Web Cam: These are fairly reasonable to purchase, either at home or abroad. You'll just need to download a program for it (skype, aim, yahoo), as will the people you plan on talking with.
10.) Pay-As-You-Go Mobile: Buying a pay-as-you-go phone overseas was one of the best investments I made. I didn't realize what a good idea it was to have one until they informed us at orientation that most students purchased them. The phones themselves are relatively cheap, and calls within the country are inexpensive, too. When you buy the phone you can get an international sim card if you're going to use it to call home occasionally. Also, I know my phone had a feature where I wasn't charged for incoming calls...so have people call you instead :)