Microsoft has acquired Skype, the popular Internet telephone service. It’s not yet clear what effect, if any, this will have on current users. But in case you’re curious, here are a few popular alternatives to Skype:

ooVoo: This service provides users a way to voice and video chat with up to six people at a time. You can make calls through a desktop client, a browser or over mobile on WiFi, 3G and 4G.

Google Voice and Video Chat: This is hard to beat for convenience. It’s right there in your Gmail and can be used for voice and video chat with any other Gmail user. In the U.S., calls are free until 2012, and international rates range from 2 cents a minute to $6.90 a minute depending on where you’re calling.

FaceTime: FaceTime may be limited to Mac products, but it still lets users chat between iPhones, iPods, iPads and Macs for free. FaceTime offers a totally immersive video calling experience — controls and window frames disappear leaving a clean call interface. The app costs .99 in the Mac App Store.

VoxOx: Like a combination of Skype, Google Voice, DropBox and TweetDeck VoxOx offers unified social network chats, video calls, file-sharing and a unified Google Voice-like number that will ring all of a users’ phones. Calls are 1 cent per minute in several countries including the United States; rates overseas range from 2 cents to 5 cents a minute. The service also has a mobile app.

Have a favorite program that we didn’t mention? Share with us in the comments.

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