I have a project at college to make an IOT (Internet Of Things) application, we will use AVR as a microcontroller, the access to internet using a WiFi or Ethernet cable was't very helpful in our application, so we thought that getting access using a SIM card will be much better, is that even possible to do or not? Thanks in advance.
Yes, its possible. What you need is GSM module like sim 900. You can use USART/UART to communicate with module. It provides a set of AT commands which can be used for getting the contents of a web page and posting variables through a GPRS connection.
Various open source libraries are available for Arduino platform. You Can start from there and later write your own code or simply copy the code.