I also 'teach' quite a bit on LiveMocha. By teach I mean correct other people's English. I've learnt a few languages and what I notice is that people tend to read/pronounce letters/words exactly the same as in their own language, when they shouldn't. I think you have to 'forget' everything you ever learnt in your own language when learning a new one. If you get stuck and hung up on it, you'll never learn the new pronunciations. Also it's interesting that for a native speaker, they know how to pronounce words but they don't always know how to spell them (and have to guess a lot of the time) but for an ESL learner, it's the other way around. Usually they know how to spell the word but they don't have a clue how to read/pronounce it, and have to guess.
I notice that non-native English speakers have a lot of trouble with the schwa sound which exists in almost every single world. They also have trouble with stress on certain syllables but can you blame them? English is really hard to read when you think about it as there doesn't seem to be any rules. The same letter is pronounced differently almost all the time! I also noticed the same mistakes come up time and time again like 'woman' and 'women' being pronounced exactly the same.
I guess for me, I'm obsessed with having accurate pronunciation so I listen to French all the time. Of course I listen to Pimsleur and other learning devices regularly, but also French radio, pop songs, random clips I find on YouTube, etc. However, I only prefer to listen to native speakers where possible. I pay attention to the sounds that don't exist in English so I practise those more. The French 'r' really isn't that difficult for me anymore and I don't have to think so much when I read. I am VERY thankful French does not have the rolling r like in Spanish or Italian (or many other languages such as Russian, Indian, Middle-Eastern and African languages) because I have been trying to do that for so long and I don't think it's possible for me :(