The best replacement for teamspeak is skype.

The best alternatives to teamspeak are rated as following:
★★★★★  skype
★★★★★  mumble
★★★★  vent
★★★  ventrilo
★  raidcall
★  razer comms
★  c3
★  vent which is better
  steam chat
  xfire
  ventrilo server
  gamevox
  roger wilco
  ventrilo better

Your alternative for teamspeak is not listed? Suggest!
Speaking about teamspeak, one probably shouldn't forget about overwolf.

Other search terms related to teamspeak and their ratings are:
★★★★★ overwolf
You have in mind a companion for teamspeak and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of teamspeak in all years. Click on graph for more.
teamspeak
skype
mumble