Pronunciation tips from the BBC
http://www.bbc.co.uk/worldservice/learningenglish/grammar/pron/

English Pronunciation 
http://international.ouc.bc.ca/pronunciation/
Excellent online pronunciation help from Okanagan University College.

Tongue Twisters

PIZZAZ! Tongue Twisters 
http://darkwing.uoregon.edu/~leslieob/twisters.html
Tongue twister activity from Leslie Opp-Beckman.