Ben Maughan over at Pragmatic Emacs has a nice post on the dired-filter package. The idea is that you can filter the files that will be displayed in your Dired listing. Take a look at his post to see how it works.
You can do the same thing without dired-filter by marking the files you want to see, possibly with a regexp, inverting the markings, and then killing the marked files. That’s a little confusing because “killing” the marked files really means deleting them from the listing not deleting them from the file system. See this post of mine for the details.
Still, the dired-filter package seems easier to use. Maughan has it mapped to / so you need merely type the / and your filter string. That’s conceptually easier than marking the files, inverting the markings, and then killing the marked files.