Tools used by developers to cooperate with customers

Hi everybody!

I'm looking for a tool to support design, fron-end and back-end developement projects to use by project managers cooperating with clients and graphic designers or developers. I thought this could be the right place to ask because of such a big community of beggining and experienced coders and designers, I hope I put my question into right category.

From my experience it's hard to plan especially visual side of project based on words, in most cases it leads to numbers of corrections which might be cost inefficient. Could anyone recommend me some webtools which could be used by clients to simply organize their websites in terms of design elements and content? Tool should allow clients to drag and drop predefined elements of a webpage, changing their size, colors, adding comments and marks, etc.

In addition, could you recommend me some analogical tools to support backend developement? This kind of tool should allow clients to easy design diagrams and describe functionalities and their rules (if - then) they want to get.

I would be greatful for share your experiences, advices and recommendations. Thanks in advance :)