An interesting resource for writers looking for markets is Duotrope's Digest. You can input the type of writing you want to sell (e.g., short stories in the genre of mysteries) and it will tell you who is looking for those. It does skew toward smaller publications (especially in the sci-fi genre) and less traditional publishers, but it's worth a look, especially for writers of short fiction and poetry. For bigger, more mainstream magazines and book publishers you're better off consulting the Writer's Digest annuals.