In the Monster Manual under 'Planetouched'.
Off the top of my head?
+1 ECL,
+2 racial bonus to hide and bluff. Ability to cast darkness once per day as a 5th level sorceror or as their character level, whichever is higher (I ammend this to give every Tiefling access to a 2nd level spell- so some might have darkness, some might have.. web or something).
+2 Dex, +2 Int, -2 Cha