The city spent $4,838,967.64 during the month of December. Usually these are done every two weeks, but the check register needs city council approval, and the holidays threw off the council's meeting schedule a bit.
But here's how the spending breaks down: Click here for the full check register. 
Smallest expense was $5 for mileage reimbursement and the largest check was $595,547.80 cut to Health Alliance for employees' health insurance. I believe Health Alliance has won the "biggest check" award in at least a couple of these posts.
UPDATE: Looking at the register again, I see I missed what was really the biggest check -- the city paid $976,570.13 to MACC of Illinois for Boneyard Creek improvements. Easy to miss, but it's on page 30. Like Health Alliance, I believe the contracting company has also won a couple "biggest check" awards.