Websites
When researching Victorian Poets, your best bet is the Victorian Web, which serves up a ton of articles, links, and biographical info.
The Poetry Foundation is another great resource on poets and their work. The Hopkins entry is no exception.
Here you can read about the village and its thirty (count 'em) residents.
Video
Here's a collection of appropriate photos, playing over a rich reading.
Here's a video with footage of places that Hopkins would have known well.
Audio
Here's a calm, capable reading.
Here's a recording of the poem, performed at a charity event put on by Princess Grace of Monaco.
Images
Here's the go-to image of Gerard Manley Hopkins, seated at his desk.
Check out one of the few photographic images of G.M.H.
This painting looks to be inspired by "Binsey Poplars."
Articles and Interviews
In case you thought Hopkins was overreacting to the loss of a few trees, check out these articles on pollution during the Victorian age in England.
Books
Here you can get the whole kit and caboodle (er, poems and prose, in other words).