Angie asked me to post some pictures of my footies that I was talking about in the "socks for sneakers" thread. So here they are. Both of these stay on my heels fine with most of my shoes (I do have one pair of oxfords that is a sock-eater, so I use fashion tape to tape the footies to my heel when I wear those.)

1-2 are the mesh ones I was wearing today. I am wearing them in photo 6, and you can see they do not show over the sneakers. I also wear them with my oxfords a lot. It's a minor miracle that I have not poked holes in the toes of any of these (I have 2 nude and 2 black pairs) after several years, as I tend to get holes in my sock toes inside of a year. These are several years old but I think they may be these Anne Klein ones, although mine have a little cushion inside. I may order the Anne Kleins to see.

http://www.zappos.com/anne-kle.....shion-nude

3-4 are the smartwool Hide and Seek socks. I haven't had these for as long as the other ones but so far they are holding up well. I do find them a bit too warm for summer. These also don't show in my oxfords or sneakers. They come in sizes, which is nice if you don't have medium sized feet.

http://www.zappos.com/smartwoo.....steel-blue

Some things to note:
-- I have very low volume feet. You can see in the side views just how flat they are. On someone with a normal or high volume foot, they'd probably not come up as high.
-- I don't wear low vamp shoes like ballet flats or loafers, so I have no idea whether or not these would show in those types of shoes.

--You need footies to fit tight. If they are at all loose they will fall off!
--In general, I think you need to look for footies that are, well, foot-shaped. By which I mean, they should have a sole and a heel and a toe area. (Like regular socks.) I've seen some footies which are basically like 2 flat pieces sewn together, with a seam down the middle, which, aside from being super uncomfortable, do not resemble the shape of a foot AT ALL.