Links

NowSMS | SMS Gateway, SMS Server Software, MMS Gateway & MMSC   - Details
NowSMS supports a wide range of SMS and MMS protocols, and simultaneous connectivity to multiple SMSC and/or MMSC connections. Applications can use standard protocols such as HTTP, SMPP, SMTP and MM7 to interface with NowSMS, or they can use sample APIs provided for PHP, Java and command line interfaces.

Kannel: Open Source WAP and SMS Gateway   - Details
Open Source WAP and SMS Gateway

Blast SMS   - Details
Send Bulk SMS text messages worldwide from your PC, Web, or Application. Cheap mobile marketing. Reseller options available

123bulksms   - Details
Bulk SMS messaging services and SMS Gateway connectivity provider.