Google Voice - Google Voice gives you one number for all your phones, voicemail organized in an email format, free...

Lookup by Twilio - Know the details behind every phone number

TextMe - TextMe is a free calls and messaging application at both local and international levels.

Ring4 - Manage business phone line as easily as you manage emails, in the cloud. Ring4 provide you with a business line and video conferencing solution.

Talkatone - Android App on. Google Play. Stop paying for cell minutes, texts & landlines; Turn your iPad or iPod touch into a phone; Call/Text even in areas with bad cell coverage; Call/Text when travelling without paying for expensive international minutes.

Shuffle - One Phone, Multiple Numbers