pesticides and all sorts of nasties come in on the bottom of soles, having an impact on the health of people living in the house, I follow Japan's shoes off rule. And now that I tend to spend a lot on socks, I really appreciate a good pair of slippers, even in warmer weather.
Acorn offers a ton of options including vegan and eco friendly slippers. I tried these Earth Roamer slippers (shoes, actually, but I've been wearing them as house shoes) made with recycled PET, and they are warm and cozy and very supportive. Warm house shoes are imperative for me to keep the thermostat turned down and for supporting my feet while spending hours in the kitchen on a hard floor.
Slippers make a thoughtful and practical gift and Acorn slippers are available online and locally at quality stores like REI. Check them out HERE.