Skype - free IM & video calls The most obvious for a bevy of reasons. It's best to use Skype over WiFi, as it won't drain your data.

Tango Text, Voice, and Video Sure, it takes two to tango. With this app, though, you can video message a group of people with ease.

ooVoo Video Call This app really pushes the 6-way video calls, which is intense. However, it's very useful for situations where you absolutely need to share big news with multiple people.

Qik Video There are versions of Qik for pretty much every service provider, and my favorite feature is the live video streaming. As you add more and more contacts, you get a steam of videos of friends sharing moments in real-time.

Ustream Qik Video is a good for sharing videos, but Ustream is the best for watching live videos.