I'm a long time model builder (45 years) but new to building dioramas.

I've been bitten by the "bug" and have an interest in building dioramas incorporating/modifying existing models (monsters, sci-fi, real space).

I've done a Google search on the topic but get a ton of hits. Some are interesting, some worthless. Any recommendations on books or web sites?

The research I've done leads me to believe model railroaders are big into dioramas. (most web stores have diorama stuff under the "Trains" category.)

A company named "Woodland Scenics" makes "LOTS" of diorama related material.

Hobby Lobby carries Woodland Scenics but its pretty expensive. Any suggestions on a Internet hobby shop that carries this material?

For Dioramas, you will learn the most from the millitary diorama makers, check out armorama (http://armorama.kitmaker.net/modules.php?op=modload&name=SquawkBox&file=index&req=viewforum&forum_id=6&page=1), they are generally much more particular about realism than railroaders.
What you will find is that you will have to think "outside the kit", look at EVERYHING around you and think of what that could be used for at the scale you are building....... pull and old disposable pen apart, and you will probably find that every part of it could be turned into SOMETHING in your diorama.

Thorrr

i get most stuff (what i don't build or make myself) from Discount trains online/ mb klein model train stuff/ internet model trains walthers model railroad has a great site for finding stuff- but other sites are usually cheaper

hope this helps