Rob's good-sense feeding hack:
Our little guy is just starting to self-feed things like peas, etc. that we spread before him at meal time. However, most of his food ends up on the floor. So to reduce this waste we now put a cookie sheet on the floor under him that catches about 90% of these dropped morsels so we can reload his tray.
Wax paper would work as well and is disposable (a pro or con depending on your perspective). Past hacks have also suggested old vinyl party tablecloths as highchair mats, I wouldn't think they're as easy to clean.