video conferencing

ooVoo

Love staying connected with friends and family members around the world, but international calling costs are affecting you adversely. Well, ooVoo is the solution to your misery. This app is the first major cross-platform IM client that works not only on different platforms, but also on PC and Mac. Developed by Oovoo itself, this app really takes the crown from its other competitors as accessibility is the name of the game here. So now, users are not locked to only Android or iOS, but can enjoy being in touch with anyone, anytime and anywhere. Simplicity at its best.

Skype – make free calls, IM & video chat online

Skype is a multiplatform software that enables users worldwide to communicate online via voice, video & IM. It's currently the biggest and, in my opinion, the most user-fiendly software of it's kind "responsible for 8% of global international calling minutes, and with its users making 3.1 billion minutes of calls to landlines and mobiles in the third quarter of 2009".