I would imagine that Google is using the number of +1 a company receives as a datapoint for search ranking. I am pretty sure I read somewhere that your personal +1 influence your search results, but I am not sure if overall +1 numbers influence non-personalized results.
I did some research and I found many domain industry Google+ pages. I am sure these companies and websites would appreciate it if you gave them a +1, especially if it helps them with rankings. If you use Google+, it could also be a good way to stay connected to learn about special offers and news.
The domain companies I found are listed in alphabetical order.
- Buy Domains
- Domain Guardians
- Domain Sherpa
- Dot CO
- Dot ME
- Drop Day
- Go Daddy
- Network Solutions
Feel free to let me know if I missed a domain industry company, and I will add it to the list.