Very Basic trigger:
Events
Unit - A unit owned by *Neutral Hostile* (change that to the team that the creeps are on) Dies
Actions
Item - Create Tome of Experience(change to whatever) at (Position of (Triggering unit))
Under Actions you could add lots of different items, but I think that the may drop all the items. There is a way around this, but unsure of it at the moment.
-Husky