I was in the need to interface an Arduino board with 3v3 level logic (to use the great JTAGEnum !) so I decided to build this simple level shifter shield. It is based on TI's TXS0108 (8bit level shifter) which provides bidirectional level translation and can accept 1.2 to 3.6 on one port (A) and 1.65 to 5.5 on the other port (B). The shield has just one shifter wired to Arduino digital port:
schematic and board files (in Eagle format).