Any reliable site where *hardware* engineers can be hired for small (work-from-home/telecommute) projects?

For software hackers/developers there are many.

However, I need a hardware guy (or girl?) for a relatively small project.

Is there a site where I can search for people and see ranks, recommendation, etc.?

Harware engineers, mechanical engineers are less likely to contract. You you might have a better chance finding is a contract manufacturer or contract design firm.

You will have a hard time finding what you are looking for on a contract basis because:
1. Most good mechanical engineers have full time jobs (which are secure)
2. Hardware engineering varies greatly, and can require a huge investment in research and labs, this is very different than software.

If you are price conscious do your research in Singapore, Taiwan, S Korea and other south east asian countries that have a good reputation for this type of work, and respect your your property rights.