Not sure if you need to have a standard Vonage VOIP account to use this, but its another option -
http://www.vonage.com/features.php?f...neo27o2ae12n00
Softphone is engineered to operate with the following web-enabled equipment: PC's, Mac's, Laptops, and PDA'a (Windows CE based devices only).
Softphone is $9.99 per month for 500 minutes, 3.9 cents a minute after the first 500 minutes, and $9.99 for an activation fee.
For any other information about Softphones, please visit
http://www.vonage.com and view all of the features that come with softphone.