These domains were checked by me manually. I had posted it on my website for a week now. Register as many as you want. 4 Character .Co List 5 Character .Co List You can use GoDaddy Bulk Order feature to check up to 500 domains at a time to see if they're available.
I did check most of the words. Most of them are already registered. Here's the list I used: 2-11 letter words list