Vonage has been horribly unscrupulous when it comes to dealing with publishers, but they've earned all kinds of accolades with consumers. Cheap, effective, pretty consistent, and did I already mention cheap?If you travel overseas, it can't be beat. You can have a US phone number, no matter where you live in the world, as long as you have a high-speed connection. Just plug it in and you're back in the states for most every purpose.
If you're locked in the states, it's still the best. Call all fifty-states without ever paying a penny for long-distance, and you won't pay long-distance to call Canada, Guam, Puerto Rico and most of Western Europe.
It's a fairly consistent service, rarely gives callers trouble, and is easily half (or less) the cost of traditional telephone service.