Here’s a preliminary list of the hottest mobile payment startups.  Feel free to add to the conversation:

Carrier Billing

• Boku (Paymo)
• Zong
• Payfone

Purchase in App (not billed via carrier)

• Apple (iTunes)

Contactless / Mobile Contactless:

• mFoundry’s mPayments
• Bling Nation
• ViVOtech

P2P Transfer

• Obopay
• PayPal Mobile
• Venmo

Mobile Checkout

• Square
• Verifone

China

• UMPay
• SmartPay
• LianLian

India

• Paymate

Philippines

• Globe GCASH

Japan

• Mobile Suica
• Edy

Reference: GusFundler