While Chris Polk has been the Eagles undrafted rookie to get the most ink, for me the most intriguing has to be Cliff Harris. He didn't play in 2011 because he had affinity for driving way too fast and getting high, but in 2010 when he was still on the Oregon Ducks he was fantastic.
That year, Harris had 5 picks, returned 4 punts for TDs and led the nation with 20 passes defensed. I came across his highlight reel from 2010 and it's impressive. It will be interesting to see how he responds after a year off and whether he's the same player... but if he is this is a potentially major talent that the Eagles have added for nothing.