My favourite quote used by a company is "Just do it" from Nike.
I just discovered a similar one-liner that deserves to be shared:
The person who says it can't be done shouldn't interrupt the person who is doing it.
I found the quote on the Google Sketchup website. They attribute it to the wall of the Mountain Rose Cafe (Winter Park, Colorado). Wherever it originated from, it's spot on.
Do you have an inspirational quote? Add it below in the comments.