I like the baby wipes idea - I'm going to borrow that one!
I'd be barefoot all the time, if I could (safely). We keep a rug by each door, and that's generally enough.
We also have a light beige carpet. Easy enough to spot clean if something gets tracked in - just use a little oxyclean and rinse with a clean cloth. An old sock works, and then you can just throw the sock away when you're done. But really, by the time you walk across the concrete sidewalk and through the grass and then rub your feet on the mat, vacuuming works pretty well. We've been in the house ten years, and people are surprised to hear our carpet is original to the house. (We're saving for hardwood floors, but things keep coming up....) But then, we have no dogs or cats who are ALSO tracking things in!
Incidentally, the "No shirt, no shoes, no service" signs are NOT a health code thing - it was an effort by businesses to keep hippies away. So you really could go barefoot out and about, if you were so inclined. Most business have given up the old signs. (Personally, you never know WHAT sorts of things are on the floors in public spaces, though, so I don't even let the kids go barefoot on the playscapes in McDonalds or whatnot - socks or no play for us! You should see how nasty the socks get....I don't want that junk on their feet! No, thanks barefoot outside, though, is different in my mind - nice, clean grass or good, honest mud for us!)