Jesus looked up and saw the rich putting their gifts into the offering box, and he saw a poor widow put in two small copper coins. And he said, "Truly, I tell you, this poor widow has put in more than all of them. For they all contributed out of their abundance, but she out of her poverty put in all she had to live on." – Luke 21:1-4 (ESV)
The widow serves as a warning. In the passage right before this one, the scribes are condemned for (among other things) devouring widows. Right away, a widow is giving money – money she needs to survive. One can't help but wonder, is this another instance of a widow being devoured? During the Middle Ages, wonderful works of religious art and architecture were built by taxing and deceiving the poor under the guise of 'giving to God'. We should taken great care when we ask for money.
The widow also serves as a model. Regardless of the intentions of the scribes, the widow gives out of her poverty. To give sacrificially shows our dependence upon the Lord and our acknowledgement that He is the one who provides. The widow gives at the "Presidential Level" with her 2 coins while the others are merely giving at the "Lukewarm Sponsor Level" with their gifts. We should give our money generously towards items that have eternal significance.