Question re dungeon designers

Asking for a writer friend

Does anyone know any great pc software for designing dungeons and areas for roleplaying games?

I used to have some success with Dunjinni - they do a demo version so your friend can try it out if they like the look of it http://www.dundjinni.com/info/demo.htm

I think that Dundjinni is good for existing PNG files to use as environmental pieces. I often use Gametable for my dungeon design and it works for my needs. I know that Venatus Maps uses Photoshop and is just good at layering and the art involved.

You might try cartographers guild. Lots of amateur as well as commission work on there.