How can we improve and motivate our help desk staff?

Pay them better. Offer incentives on how quickly calls are resolved.

Scottgem is right, people like money. Things like office parties on slow days and making the office look a bit better might work too, but... you know... money!

Of course by the rating given above it sounds like you don't want to spend anything to get morale up, correct?

Well obviously three people don't know that it was a bad answer so that makes YOU wrong. I grant the answer was a bit flip because its so obvious. But it still was valid nonetheless. There may be other ways to motivate people, but what motivates them most is remuneration.

Let me see, flexable hours, better parking for someone who is employee of the week. Get them better computer equipment, telephone equipment and be sure they are not overworked. Have enough employees for the work load. But bonus money for meeting certain goals is almost always the best. But it appears you want something that does not cost money.
Make sure the work area is bright and cheerful.