Wanted to add that Skype is great for talking to other Skype users.
What's even more handy is SkypeOut feature, since you can call anyone with,
Of course it does cost around 3 cents to call US number and some countries can be really expensive, but for most countries it is a viable option.

Then there is SkypeIn which is pretty damn cheap for answering service AND your own call-in number, last I checked it was $4 a month for both. Oh, did I mention that people can call you at at that number and if you are online in Skype you will get the call. Pretty cool, eh?

Man, I sound like a talking ad for Skype, in fact I really dislike the fact that eBay bought Skype.