I own one of those smart cards that were often used for illegal viewing of encrypted video signals (those were the days). It contains an Atmel AT90S8515A processor and an 8k EEPROM memory AT24C64, which gives the card adequate processing power for numerous other purposes. Other card types exist, under different names, with different processors and EEPROM sizes.
I intend to put my card to a better use one day (hopefully).
It may well run a tiny TCP/IP stack which in turn will make it possible to create a small web server with it :-)
In the mean time I keep the card specific details on this page for future reference.
The diagram above is the circuitry that's embedded in the smart card. A total of 3 I/O lines are accessible from the outside and can be used for all sorts of activities. To make a web server on this card we need at least 2 lines for serial communication to a router that accepts the SLIP protocol. This leaves us with one I/O line to play with, which is plenty! This I/O line can be used to interface with a digital thermometer from Dallas Semiconductors, or to connect to a hit counter, or simply an activity LED.