yes, click on the city and then look at the bottom left part of ur screen (with the city being selected) you will see the queue there  and a small x above the unit/building that is in the queue

EDIT : just alittle sooner and i would have been first to reply !! The world isnt fair

Yes,  With a city selected, there are tabs along the left side of the info panel (at the bottom of the screen).  One should be "buildings" and another "troops" or something similar.  You can see what's in the queue and click on the "x" over ones you want to cancel.

Edit:  I'm the FOURTH response?  Dang.