What is a cheap but effective way to fix a cracked cement floor myself?

The floor is in the laundry room and is completely unlevel on both sides of the crack. the crack is about half an inch wide all the way to the bottom of the cement and 3 feet long.

Call three local contractors specializing in mudjacking for a free estimate. Be honest and tell them upfront that you want to fix it yourself and ask if they would be willing to come by in their spare time for some advise. Then if it's too big of a job you already have the quotes and have met the contractor.

With a crack that deep, I would use thin-set tile mortar. You can find it in the tile section of your home improvement store. Make it the same consistency it tells you for adhering tiles. Trowel it into the crack and quickly jiggle the trowel to "liquify" it enough to get it to flow deeper into the crack.

If it is lower than you want after it dries, you can then use a self-leveling concrete repair that comes in caulk-gun tubes.

dont use mortar it has no strength as a patching compound. use portland cement and sand or concrete caulk. as for leveling the floor you have a few options. an inch topping of portland cement which will probably crack again if the floor is still moving, or the floor leveling compound mentioned above...may want to replace the floor if you plan on living there awhile...

without busting it all our and re-pouring or jacking each side to level and "shimming" the slab, your options are as follows:

You can get cement patch. you can get it in a tube or a small bucket depending on the amount you will need. this patch is flexible and will flex as the slab moves with the temperatures. dig out as much dirt as you can from the crack and fill it level with the patch. then you can leave it and call it good or you can take it a step further and get some floor leveling compound and pour a thin coat (about 1/2") over the top of the entire floor to level it. later you can tile or lay vinyl flooring right over this.

however, if the crack is new, i would recommend waiting a few months to see if the slab continues to move as there could be a concerning underlying issue such as a sinkhole or root system causing the cement to buckle.

First you want to get a steel brush which is thin enough to fit inside the crack. This will be used to clean out the crack. Next go to your local home depot/lowes and ask for a concrete filler. They will give you exacctly what you need, this will seal your crack.