Contra-what?

Last night when I got home from playing soccer, I was too keyed up to go right to bed. So I ended up browsing the Internet for a while to unwind.
I was browsing Del.icio.us and found this interesting article on one of the stranger aspects of the English language. Contronyms. Contronyms are words that can mean opposite things based on where or how they are used.
Some of my favorites are:

• apology - admission of fault in what you think, say, or do; formal defense of what you think, say, or do
  
• screen - show, hide
  
• consult - ask for advice, give advice
  

You can read the entire list and the article: Fun with words