I have a pair of slippers lined with fleece. They are very comfortable, but my feet get SO hot when I wear them that I have to slip them off occasionally so my feet cool down.
While flipping through the LL Bean catalog, I came across a pair of slippers that were in a flip flop style. They were made of suede, and lined with the same fleece as my regular slippers, but there were open like a flip-flop. I decided to try them.
These slippers are very comfortable! The fleece on the inside is very warm and easily moulds to your foot after wearing them only a few times. The flip-flop style makes them really easy to slip on and off. The sole is very hard, so they can easily be worn outside. They are available in a lot of different really pretty colors.
On the downside, the sole is relatively inflexible so it is hard to sit on the floor cross-legged while wearing them. The sole is also sort of rubbery, so I sometimes trip on the carpet in front of me if I don't pick my foot up far enough. (Yes, I am a bit clumsy so if you are not, this may not be an issue for you.)
They do not keep your foot as warm as a traditional slipper, but if you are like me and easily overheat then these might be for you.