How to get a linux directory listing for files beginning with a certain letter that doesn't descend into subdirectories?

Ah, I just found it on the 6th reading of the man page. It's the not-so-sensibly named "directory" parameter

ls -d d* 

I believe another interesting solution to be,

ls | grep ^d

Offers the flexibility of regular expressions.

find . -maxdepth 1 -name d* -type f

Okay, using find here is a tad of overkill. Just a tad.