I’m sorry for the poor quality of this photo. The white on the right-hand side is actually a whiteboard in the teacher’s offie that I have to lift away from the wall.
This is a Tokay Gecko. It has a very distinctive call which is worth listening to: http://en.wikipedia.org/wiki/File:Mating_call_of_a_male_Tokay_gecko_(Gekko_gecko).ogg
Apparently, it can be quite dangerous; if it bites you it doesn’t let go for up to an hour or more. This one seems to be quite small – it’s about 20cm.