I just set up a new system with my cages a couple weeks ago. I built the mist/drip system for about $60 with materials from Lowes. I originally had catch trays but I had the overspray problem as well. I built the PVC pipe rack and all of my lighting sits on top now as opposed to my cages (makes cleaning cages much easier), the mist system tubing is also attached to the pipe. I went to a local plastic distributor and bought a 4'x8' sheet of corrugated plastic like the kind you see on the roadsides used for campaign signs. I cut it down, bent it into a V-shape and drilled several 5/8" holes in the lowest point of the V. I then put a drainage gutter underneath it at a slight angle and positioned a 5-gallon bucket to cath the water. It's all on a timer and it works great. It pretty much eliminated the overspray problem, you just gotta fine tune your mist heads to point in the proper direction. I know this would be an overkill for 1 cage on a dresser, but I'm sure you could simplify it.
http://www.youtube.com/watch?v=lkPR_FCLwAM