-- Available through April 29, 2011 
Tell me the difference between allusion and illusion.
See how Brian Cleary explains the difference:
ALLUSION  vs. ILLUSION? An allusion is a (usually indirect) reference to  something; It’s like a hint or suggestion. An illusion is a false  impression or idea, in which one attributes reality to something unreal.  Examples: In an ALLUSION to her career as a dancer, she named her cat  Baryshnikov.  It is only an ILLUSION that the stock market is  recovering.