You don't have to download and install anything. No, but some are, so why should you pay if the quality is not that much better. Use the Free stuff first.
Phone calls over the Internet at no additional charges.
Really Easy Voice NOT FREE - Very easy. Free - You will get your own Internet Phone number. FREE - Must be integrated with ICQ . Used to send a telephone voice message to ICQ contacts. Net2Phone NOT FREE - To call any telephone in the world.