Content aware- 

Use the marquee tool, lasso, or spot healing brush to select an area that you want to be filled with background.  With the marquee or lasso hit delete, select content aware, and hit enter. With the spot healing brush just click and drag on what you want.  If you want to make a panoramic photo, then combine all of the photos, select the background and use the marquee tool to select the entire image, then hit delete.  

Be careful with this tool because it can fill in background with an image you did not want there.

Links:

(prerelease video)

http://www.youtube.com/watch?v=NH0aEp1oDOI

(parody)

http://www.youtube.com/watch?v=3ScWu7pG7r0

-Mike