In regards to an early post as to what consitutes a really good short, Witrack reccos. two on Atom Films to check out. The 3 min. Trick from Mike Mohan:

This is a movie that will stay with you long after you watch it. A young girl who thinks she's got it all together invites you into her world to learn her terrifying secret. Be sure to watch it through to the end.

The other is this one:

The 8 min. The Trinket-Maker by Paul Daley:

Wendell's home in the clouds is unusual and beautiful, as are the fascinating objects he creates, but his is a lonely existence. When a chance encounter seems to offer him an earthier alternative, Wendell is faced with a dilemma. Should he dare put his feet on the ground?

Check them out and see if they really grab you, stay with you.