Indeed, there are many fun uses for paper towel tubes. Here are a few from a recent project night at my grandson's school. Oh, yeah. Teachers know how to collect STUFF.
Other uses: tunnels, molds (ice, candles, clay, sand), collage pieces, bracelets (slice lengthwise), ponytail holders holder, swords (you know they always end up as a weapon), stamp (for circles)
The list could very well be endless. :)
Note: Please use paper towel or wrapping paper tubes, not TP tubes. I just feel better that way. No potty germs to consider.