Cel.ly: connect with students by sending updates directly to their cell phones. Students simply send a text to the Cel.ly number provided and they will be added to the class text list. The teacher can then send updates or reminders for projects, homework, and more. Free to use.
Eyejot: send online video messages to users around the world. Free to use, webcam required.
Skype: an internet call service. Skype allows you to video or voice chat with any other Skype user around the world for free. You can also buy a Skype phone number and use it to place calls to non-Skype users. Different rates apply for international calls.