Lots of talk about PluralEyes for synching multiple tracks, and now a beta version for Premiere CS4 and CS5 seems to be available at Singular Software (http://www.singularsoftware.com/downloads.html).

Haven't tried it yet but plan to give it a go to see how useful it is. Sort of mixed reviews for the other platforms but still curious to see if it works...

Here's their page on the workflow.

http://www.singularsoftware.com/help/pluraleyes_pp/howto_pluraleyes_premiere.html