What is the easiest way to get free or really cheap tile?

Check in your area for a Re-Store by Habitat for Humanity. Mine has many tiles to choose from (boxes full)

Check you local Home Improvement stores for close-out tiles usually offered at a discount.

Tile does not have to be expensive. I agree look for leftovers, bargain, thrift options, even the best tile shops have stock they will move cheap. Consider using different tiles and making some pattern or at least a line of different color or texture. Remember your bathroom after your kitchen is the highest per square footage real estate in your home value and resale potential. Don't go so cheap as you lower your appeal.

We made some killer deals on tiles for our home's rehab: Mexican crackled tiles were discontinued at a tile distributor...we bought the last in stock for next to nothing; we made an offer, they accepted. We bought Italian glass tiles at a Restore in the next town over and bought fantastic industrial-type tiles in our town's local Restore. (These tiles were brought in by contactors who had finished housing and store projects.). Lastly, we bought a case of white trim tiles at yet another Restore for $8! As you can tell, we spend quite a bit of time visiting all of the local Restores. It's incredible what you can find at the local Restores, especially in the bigger areas where contactors donate.

Find a nonprofit organization that takes in donations and 99% of the the they have more than they can store. They aren't allowed by law to resale it, but will take a donation. Homeless mission here, we have the old church next door using it for storage and that's how we do it. We gave away over $50,000 in brand new household items that were donated. From floors to ceilings. You name it, we had it. Sometimes your hardware stores have returns that were opened or a tile missing, wrong color paints mixed etc etc and they 90% discount those items.

Restore for Habitat for Humanity! Can't beat their prices AND it's for a good cause