user3163: I'm fairly new to this and I need some help before I buy anything...
If I understand correctly I can buy an arduino, couple of shields and just stack them one onto another if they are compatible...
I'll be doing some work with an arduino and I would need both WiFi and GSM shields but I'm not sure if they're compatible... On the arduino.cc I saw that they both use pin 7 (GSM as modem reset and WiFi as "handshake") 
Is there any way I can use both of the shields even though they use the same pin?
Thanks

user6732: You can still use both of them although you'll need to buy another piece to make it work.
This is called the Go-Between Shield and it basically lets you re-route a pin to a different one.  You will need to change the pin number in your code to the one you re-assign that signal to but it will still work.  
The signals you listed that go on that pin are very incompatible, as in if you try to do it, you'll have problems.  Every time your Wifi shield will try to connect to something, your GSM shield will reset.

user27110: If you will be using Wi-Fi, instead of buying a Wi-Fi shield and a GSM shield, simply buy an Arduino Yún (which will substitute the Arduino and WiFi shield) and connect the GSM shield to it.
From How to use the Arduino GSM shield with Arduino Leonardo, Arduino Yun, and Arduino Mega, it shows you how to connect the Arduino Yún with a GSM shield and to use them without any problem with the help of jumper.

3163: <p>I'm fairly new to this and I need some help before I buy anything...</p>

<p>If I understand correctly I can buy an arduino, couple of shields and just stack them one onto another if they are compatible...</p>

<p>I'll be doing some work with an arduino and I would need both WiFi and GSM shields but I'm not sure if they're compatible... On the arduino.cc I saw that they both use pin 7 (GSM as modem reset and WiFi as "handshake") </p>

<p>Is there any way I can use both of the shields even though they use the same pin?</p>

<p>Thanks</p>
 6732: <p>You can still use both of them although you'll need to buy another piece to make it work.</p>

<p><a href="https://www.sparkfun.com/products/11002" rel="nofollow">This is called the Go-Between Shield</a> and it basically lets you re-route a pin to a different one.  You will need to change the pin number in your code to the one you re-assign that signal to but it will still work.  </p>

<p>The signals you listed that go on that pin are very incompatible, as in if you try to do it, you'll have problems.  Every time your Wifi shield will try to connect to something, your GSM shield will reset.</p>
 27110: <p>If you will be using Wi-Fi, instead of buying a Wi-Fi shield and a GSM shield, simply buy an Arduino Yún (which will substitute the Arduino and WiFi shield) and connect the GSM shield to it.</p>

<p>From <a href="https://www.arduino.cc/en/Guide/GSMShieldLeonardoMega" rel="nofollow noreferrer">How to use the Arduino GSM shield with Arduino Leonardo, Arduino Yun, and Arduino Mega</a>, it shows you how to connect the Arduino Yún with a GSM shield and to use them without any problem with the help of jumper.</p>
