Source: http://lifehacker.com/5897735/crowdcall-is-a-simple-way-to-make-group-calls-from-android-and-iphone
iOS/Android: Group calling isn't something most of us need to do often, but it comes in handy when you're trying to make plans with a bunch of people or when you're making the rounds for holiday calls. CrowdCall simplifies the process by making it easy to make calls to up to 20 people directly from your iPhone or Android phone.
The nice thing about CrowdCall is that only one person needs the app to use it so you don't have to worry about getting everyone set up in front of a computer or having their apps in order. To set up a call you tap a plus symbol and start adding people from your contacts list. You can save that list for later so you can quickly bring up sets of people. CrowdCall is supported by ads and with that comes a slightly annoying text message that follows the call, but as an annoyance to an otherwise free app and service it's a reasonable trade-off.
CrowdCall | via The Next Web