jQuery Forum

This is exactly the purpose of using jQuery.noConflict(). It allows
you to run multiple versions of jQuery and even other libraries that
might use the $ variable.
If you're using multiple versions, just make sure to include the
appropriate plugins at the correct times (only load plugins for a
specific version when that version is the one that is assigned to the
global jQuery variable).

I put together an explanation of how this works, along with a demo:
http://blog.nemikor.com/2009/10/03/using-multiple-versions-of-jquery/
Hope that helps.