Thanks for the replies guys.
akry - The more I think about it, the more I think that the motor mount might be worn out or something. The motor actually moves a good 2 inches or so in the engine bay when it is shifted in or out of gear. 'Course this is pure speculation on my part...
stevebfl - I was taking pot shots in the dark with my guesses
So there are two problems that need to be addressed now. Is there any way for me to visually check the belt tensioner on the serpentine belt myself? I don't think I can come anywhere near to explaining this to the local techs... and would you know if I could do the same for the motor mounts? Should I look for cracks, debris, etc. around the areas in question?