It's an ambitious project started from some italian hackers with high skills in gsm technology.
http://wiki.thc.org/gsm/The documentation is all in english don't worry and the project is quite active.
We want to bring together all the folks that are interested in building a gsm receiver.
GSM is the worlds largest mobile phone standard. GSM 2.5 is currently in use and some countries are (slowly) migrating to GSM 3 (3G, UMTS, ..).
Available GSM analyzer cost a shitload of money for no good reason. Our goal is to build a GSM analyzer for less than $1000.
From there we have an unlimited number of possibilties of what we can do:
1. Understand GSM and verify the implementation and what kind of data is flying through the ether.
2.
Analyzing debug traces from dct3 mobiles See DCT3 Debug Trace Project.
3.
Track/Locate a gsm mobile. This can be done with just 1 (!) GSMSP receiver.
4.
Crack A5 and proof to the public that GSM is insecure. See A5 Cracking Project.
5.
Create our own baby cells. Imagine running your own BaseStation in your house, university campus, convention or local area. Calling inside the baby cell would be free and calling others via an asterisk/skype gateway would be extremly cheap.
6. Analyze and learn about OTA messages that the operator use to upgrade our phones (without our knowledge). (That's sim toolkit, ringtones, logos, ...)
7. We can detect if a GSM MitM attack is happening in our area. (e.g. we can detect if somebody else is sniffing a conversation in a 7+ miles radius).
A seperate Project is designing their own RF board to receive GSM signals. Please take a look at
http://wiki.thc.org/gsm/rfboard.
FORUM
Technology matters 
