Definitely Onesuite. Have been extremely happy. I use it as my primary service from my home phone. Well worth it.

If you have Vonage VOIP service, you can access it from hotels and other places with boradband connections through your laptop.

The only downsides with Onesuite are that the money expires if not used in 6 months, and they do not accept American Express. But overall, it has been excellent. There is a connection fee if you call from a payphone, but that's fairly standard.