Babies who are just learning to walk and hardwood floors are recipe for disaster (conversely pug dogs and hardwood floors are a recipe for hilarity). Non-slip sockies are an absolute must. There are a couple of ways to add stickability to sockies that don't have any.
The first is to use dimensional paint on the soles of the sockies, either in dots or in a pattern. The paint comes in various finishes for extra swankiness, and you can find it at Amazon starting at about $8.
Apparently Toronto is going through the great fabric paint drought of 'aught nine, as three different craft stores didn't have the stuff. So after some discussion I was advised to try dots of waterproof wood glue, mixed with waterproof acrylic paint. Which actually worked pretty well...
I painted onto the sockies first with the paint-glue mix then topped it off with a thicker layer of straight glue. They're definitely non-slippy, and I'll let you know how they hold up to washing.
Another suggestion I read was to use spots of latex caulking.
Whichever way you choose, I would advise 'blocking out' the surface area you'll be working on. I jammed a bit of cardboard into the sockies to protect the other side and to give me a nice flat surface. Now I can't wait for the paints to arrive so I can put paws on every pair of socks we own.