More general info on the MIFARE page.
There is a version with 3DES authentication called MIFARE Ultralight C.
Ultralight has a 64 byte EEPROM of which the final 48 bytes are for application data.
Sample tags proviced with the Touchatag (aka Tikitag) are Ultralight tags.
NFC Forum Type 2 Tag
From NFC Forum: Type 2 Tag is based on ISO/IEC 14443A. Tags are read and re-write capable; users can configure the tag to become read-only. Memory availability is 48 bytes and expandable to 2 kbyte.
NXP AN1303 (pdf) describes how to use an Ultralight or MIFARE Ultralight C as Type 2 Tag.