What VoIP service worked for you best? Which would you recommend to your friends and colleagues?

Currently the top contenders are:

• IPsmarx SIP Based Calling Card Platform by IPsmarx Technology
• Asterisk by Digium
• IXC Softswitch by IXC
• Fonolo by Fonolo
• Phybridge Uniphyer by Phybridge Inc.
• Truphone by Truphone
• FreePBX by FreePBX
• 3CX by 3CX

Vote here: VoIP Product of the year 2009.