I discovered Foot Petals on a trip to Nordstrom's a while back. I was immediately drawn to them-- my biggest problem when wearing heels is that the balls of my feet will start to ache from walking and dancing, and when wearing flats I got the same ache in my heels. I'd been searching for cushioning inserts I could slip into my shoes to help alleviate this problem. I had tried some gel inserts, but they didn't have any adhesive so they slipped around a lot and were annoying.
Foot Petals are slim and have an adhesive strip on the bottom. This means you can't change them from one shoe to another, but it also means they'll stay put. There's a variety of different cushions available: ball of the foot, heels, back of the heels (to prevent the back of your shoe from slipping or rubbing), whole foot, for small straps on strappy sandals. I bought the small strap inserts (which I used as back-of-heel cushions on one pair of shoes and it's made them wearable again) and the whole foot ones. I don't recommend those, the "one size fits all" means it's hard to hit your heel and ball of your foot at once. The separate heel and toe cushions should work better, and be a bit easier to slip into deeper shoes like boots.
There are also lots of gift sets with differtent combinations of each of these inserts all in one package (such as the Fancy Feet or Strut N Style kits). Each of the inserts come in black, grey, pink, and beige, to blend in a bit easier to your shoes (some cushions such as the toe tips come in additional colors, such a zebra stripe). And they're small and sleek enough to be worn even with open sandals.
Go to the Shop section to purchase these little foot savers, or find a store nearby to check them out in person. Your feet will thank you!