You can change the playout speed of a clip by alt-clicking on the clip near the beginning or end of the clip.
When you do this, the Mouse Pointer will change to 
to
indicate you can change the speed. Alt-click and drag out to speed up
the clip or drag in to slow it down.
You can also change the playout speed in the Clip Inspector.
A clip that has been slowed down will be marked with a 
, a
speeded-up clip with a 
.
