iOS/Android: Free messaging apps such as WhatsApp and Viber are handy for free messaging to other people with the same app installed, but what happens when you want to make a call to someone on a regular number? FooTalk is a newly-launched VOIP app which offers relatively cheap rates for calls.
In Skype-like fashion, you can call other FooTalk users for nothing, or pay a per-minute charge to call regular numbers. The app works on both Wi-Fi or mobile networks; as with any app of this type, you need to be careful of incurring data charges if you use it on a 3G connection, and the default setting is Wi-Fi only.
Rates for calls vary according to destination. Calls to Australian landline numbers are 2.3 cents a minute, while Australian mobiles cost 12.9 cents per minute. That's likely to be cheaper than your official rate if you're on a contract, but not a good deal if you have an unlimited plan. It's also cheaper than Skype's equivalent pay-as-you-go rates (3 cents for landlines, 26.9 cents per minute for mobiles, plus a 6.9 cent connection fee.)
FooTalk is a free download for iOS and Android, requires registration.