On pins and needles
Excited or nervous.The girl has been on pins and needles all day waiting for the contest to begin.
On par with (someone or something)
Equal to someone or something.The new French restaurant is on par with the best restaurants in Paris.
On paper
In theory, if judged from the written evidence.On paper, the idea seems like it will be very successful.
On order
Something that is ordered with the delivery expected at some future date.The store has several computer printers on order.
On one`s toes
Alert.The teacher asks the students many questions to keep them on their toes.
On location
A movie being filmed in a location away from the movie studio.The movie was filmed on location in the mountains.
On line
Connected to a computer.The editor is able to do most of his work on line.
On land
On the land, on the soil, not at sea.The old sailor was never very comfortable when he was on land.
On impulse
Done without planning.I bought the new DVD on impulse.
On ice
Away for safekeeping or later use, postponed.The city may put the plans for the new stadium on ice while they try to raise more money.