Hardware/workflow for HD multicam shooting on a budget
More and more cameras are including GPS time sync now that they almost all use them for location information.  I am sure you can find a camera at any price range that includes this capability.  The GPS should keep your cameras within a few hundred milliseconds of each other.

Take them for a run at Best Buy or a similar store, letting them run for a while to see which keep in sync and which only sync on start-up.

The least expensive option is to put an AC quartz clock with a continuously sweeping hand on stage and occasionally have people "sync" by bringing it into view. :-)

I just looked on B&amp;H for a reasonable camera and found this tip at http://www.bhphotovideo.com/find/newsLetter/Time-Code.jsp


  Experienced videographers will "stripe" the video tape with time code
  prior to their shoots. To prepare the blank tape to be striped, they
  rewind the blank tape to its very beginning, and with the lens cap on
  the camera, press Record and record black from the very beginning to
  the very end of the tape. Striping the tape burns time code to the
  tape, and this time code will not change when recording your future
  video footage to that tape. This can alleviate possible time code
  inconsistencies that can be created by many types of camcorders.


This may be worth a shot with your current gear.