Nikolai Golovchenko [golovchenko@MAIL.RU] says:

                     +3.3V +3.3V
       5V            |     |                 3.3V
 -------------       R     R             -------------
 |    PIC    |       |     |   SDA       |           |
 |           |-------------o-------------|  SLAVE    |
 |           |       |     |             |           |
 |  MASTER   |--|<|--o-------------------|           |
 -------------  1N4148     |   SCL       -------------
                         Zener
                          3.6V
                           |
                          ===

Questions: