I know, I'm cheap. I would say "So sue me," but don't sue me because I'm also broke.
My take on mopping the floors:
Sponge mops are yucky, and they just push the dirt around.
String mops work a little better, but unless you have one of the removable mop heads that you can toss in the laundry regularly they're also yucky.
Scrub brush and bucket gets your floor incredibly clean but it's murder on my knees, hips, and back. I do this for my spring cleaning, but I'm too creaky to be getting on my hands and knees to scrub the floor regularly.
Swiffers are awesome, but the refills are highway robbery. So, I fill a bucket with mop water (yes, a bucket. The spray swiffers cost more and I'm cheap, remember?) and toss in several of these:
Stick one on the head of your swiffer and tuck them in the gripper thingys. I use a fresh one for every section of floor I mop, and toss the used ones in the washer as I go so I don't have to put dirty rags in my clean mop water. You can also use them dry if you just want to dust.