Singular Software unveiled PluralEyes 3 back at NAB 2012.  If you aren't familiar with PluralEyes, it is a audio syncing program that took the HDSLR video editing world by storm a couple of years ago.  Read my PluralEyes review from 2010.

Some NLEs, like FCP X, offer syncing capabilities in the box; however, it's not near as full-featured as what you can do with PluralEyes 3. I caught a brief demo of it and the sync speed with tons of clips is remarkable.  Additionally, the interface is not near as clunky as the older versions.  If you want to give it a try, the free beta for PluralEyes 3 is now open.

Right now, it's only available for OS X 10.7 and will work with FCP 5/6/7 and FCP X 10.0.4 and Premiere Pro CS5/5.5/6.  Media Composer is not supported in this iteration of the beta release.

You can get it on Singular Software's website.