George Mason University built a wonderful tool for pronunciation research and learning.
The Accent Archive has people from all walks of life all over the world reading the same simple English paragraph. Go through the How To section, then there are three ways to browse for different accents, all recorded on mp3. After you try out a few (or many, I spent a good 2 hours the first time I encountered this site), you can move on to search the 2096 samples (and counting) for your research purposes. Most contain phonetic transcriptions. Resources has links to background research and related websites.
There are two ways I use this archive for teaching. I introduce it to students, and have them choose an accent, and see if they can write down the utterances. I will often get groups to try out certain areas, like India, or South America. After they try transcribing, I reveal the text of the paragraph.
The paragraph itself is a wonder. It is short, yet contains almost every sound in English, and most of the difficult ones for non-native speakers. It is a real challenge. I get my students to record the passage on the first day of class, and on the last, and compare those. The technology to do this is my next Tool.
But for now, here is that wonderful paragraph.