Where I work, once most of the candidates have been filtered out and there are only 1-5 remaining, managers get help from the senior engineers to assess the candidate's technical skills before interviewing. In my specific team we try to find code samples from github and contributions to open source communities (we love ohloh.net).
But we also do a "technical interview" with some fizzbuzz stuff. More than once we found candidates with good-looking open source patches but that couldn't implement fizzbuzz-like stuff on a whiteboard.