The British Library Sound Archive has a collection on Accents and Dialects, a great resource for anybody studying this aspect of English language. Collect Britain has a selection of over 600 sound recordings you can listen to online taken from the Survey of English Dialects and the Millennium Memory Bank. You can browse the collection here or search the collection by area, but make sure you select 'Recorded Speech' in the Object Type selection box, otherwise you will get a lot of results in other formats.
And here are a few links to similar projects and collections.
Let us know what you think of this resource, or ask any questions by leaving a comment on the blog, or by emailing firstname.lastname@example.org.