LendList - Never again forget what you borrowed from someone and keep track of what your friends borrowed from you (Android app). - raphaelm/lendlist
Magnus - Shazam for art
You Borrowed It - Keep track of who borrowed what and when you can expect it back
Masterworks - Invest in the world’s most valuable paintings.
Outdoorsy - Find the best RV rental
ARTO Gallery - The newest way to discover and buy art you love