Speech accent archive

Here's something so extensive, only a strongly supported academic could put it together: The Speech Accent Archive:

The speech accent archive uniformly presents a large set of speech samples from a variety of language backgrounds. Native and non-native speakers of English read the same paragraph and are carefully transcribed...This website allows users to compare the demographic and linguistic backgrounds of the speakers in order to determine which variables are key predictors of each accent. The speech accent archive demonstrates that accents are systematic rather than merely mistaken speech.

There are many accents in there from well-known and more obscure language backgrounds. You can spend a lot of time there listening to all those variations.