PC to telephone via IP

Hi, does anybody know if the following is possible, and what application I could use. Is it possible to make a phone call to a telephone with a PC connected to the internet. e.g. a machine continuously online using adsl or even a dial up connection to an ISP. Can I use my IP connection to make telephone calls anywhere without paying extra for them? R.C. --------------------------------- Do you Yahoo!? The New Yahoo! Search - Faster. Easier. Bingo.