Omegle is the most popular among all sites to talk to strangers. You can have either text or video chats based on your interest. This is also available for iPhone in App Store.
iMeetzu is another popular site which connects you to first random person available on chat. It also offers wide variety of features like map search, user search and registration for keeping logs. It is also available for iphone.
3. A Nice Chat
4. Getting Random