I am currently interviewing for a developer role in my company and I have had a lot of poor candidates come in so far. One of the things we have discussed is providing an online test for the candidates to fill in.
Has anyone ever used an online service like this? Even if the service charges a fee that is not a problem. I would prefer if the candidates quiz results were confidential.
Only advice I can give, If you host this online developers have access to google and, stack overflow :D, I would recommend coming with a more optimistic, but face-to-face approach to get the knowledge that someone has, under slight pressure and feeling nervous.
This will probably get you to see a little bit less than what they know, which will be a much more pleasant surprise when a new hire relaxes up and exceeds your expectations.
You might read this blog entry by Jeff Atwood: http://www.codinghorror.com/blog/2010/02/the-nonprogramming-programmer.html
He mentions a very simple website that allows you to see developers coding in real time. It won't ask the questions for you, but if you come up with some programming questions, have a telephone/online interview, and ask the questions before the candidate ever comes into the office, you'll be able to weed out the non-programmers from the potential candidates. It's located at http://i.seemikecode.com/
Of course, the above service won't ask your questions for you. You'll still have to invest 10 or 15 minutes to "proctor" the programming questions you'll be asking.