This area of interest becomes borderline management consulting, but with the tools of designers instead of business. I have made a list and done some research on this area. I think it is interesting to see designer, marketers and business professionals discuss similar problems and use similar tools, but with the jargon of their industries. These are a few design-centric firms that come to mind. I have assumed that by practices you mean firms that are working for clients not companies using a similar approach as IDEO with their internal teams.