What is this all about?

If you wish to read and write your GSM sim card, to retrieve your phone numbers or SMS for instance, you can buy a little adapter like this one for about 25$, or you can make your own. Not that it will cost you less, but it's just more fun!

First of all, you need to find the proper socket for the sim card. Once you have that, everything else is a piece of cake.
The serial port will connect to any DE9M conncetor on your PC (M-male F-Female).

Basically, the circuit uses power from the serial port through pin 4, and powers a couple of BJTs and 3 HC inverters.
Two ports generate a 3.58MHZ clock for the sim card.
The I/O line is driven by Q2 (TX) , and served back through U1C to RX.

C1 and C2 are in the order of a few pF (see any HCMOS application note for crystal oscillators).

You can use standard (DIL) or surface mount (SMT) components.
Here's a possible layout.

Have Fun with it!!!