Like the others, I tried the neoprene ones, seal-skinz socks, and the nylon ones. They either didn't work well, were hard to put on, or weren't comfortable. I would just go without, but really didn't like it.
I was constantly on the lookout for a solution to wet shoes. Climbing up a mountain in the UK, I had the idea of using plastic water bottles on the end of my shoes as a rain barrier. When I got home, I did some experimenting and came up with a gaiter/water bottle combination that works as well as or better than any of the others. I now carry these "shoe-ins" with me whenever I tour. Here is
the article I wrote about them. There easy to make and weigh virtually nothing.