The best thing you can do to learn how to understand english people when they speak is to practice. Listen to more basic messages and conversations at first, and then when you feel comfortable with those, continue listening to more difficult ones.
Here are some websites I found when i googled "english listening":
Randall's ESL Cyber Listening Lab
Listen to English around the World.
BBC Learning English | Home page
English Listening Resources - Englishpage.com
TESL/TEFL/TESOL/ESL/EFL/ESOL Links - ESL : Listening
Hope this helps!
- For Teachers