SIM800L & SIM800L EVB v2.0 - Variations and wiring - General Electronics - Arduino Forum
Amazon.com: Module,Development Board Module Kit,5~26V SIM Development Module,Fit for SIM900 850/900/1800/1900 MHz GPRS/GSM,Quad-Band 850/900/ 1800/1900 MHz - Would Work on GSM Networks : Electronics
How to Use Arduino GSM Shield SIM900 - AeroArduino.com