Off to a good start.

Future-Nine is a start-up in VOIP, clearly stating that they are still in Beta.  Nonetheless, they offer clear connections, an attractive array of features (some present, some to come), and great a-la-carte prices.  They also offer the lowest priced ongoing monthly plans on the market, and a 14 day money back guarantee.  Unlike some, they do not offer free hardware rentals, nor do they have their own softphone (plenty of free softphones available).  Connections are crisp and clear.  There is no real-time customer support, but email responses are next-day or better.  A good choice for a second line, or for a low cost North American long distance line.  International rates are quite reasonable as well.