i'll never forget the train trip i took during my first week in birmingham, england. i had just arrived for my year-long master's program, and had gone into town with my new greek flatmate, maria, who had also only been in the uk for five days.
a ticket collector came around the train, and as he was inspecting our tickets, he asked us something. knowing i was the native english speaker, maria turned to me to explain his question to her, but i couldn't. it was my first exposure to a true birmingham accent and i couldn't understand a word.
richard forwarded me this link to a bbc program, where the commentator (who's an accent trainer for actors and actresses!) spends the first portion of the show explaining and illustrating the differences between the various english accents. it's fascinating, and well worth listening to for five or ten minutes.