Hi,

Usually simple notepad or mindmapping tool is enough to store ideas and design flows. Dropbox or Evernote is the simplest solution to be always updated with your work, despite where you are.

There are 'wiki' projects, here the problem is with internet connection, however tools like MindRaider are capable to download/upload content and allow user to quick and easy edit.

Now, where I, as designer, can store i.e. GUI elements or their layouts? Some limited interaction with this kind of item would be helpful. Drawing them in MS Word or OpenOffice isn't satisfying (size changing problems). Visio or PhotoShop are too big tool for this simply task. Qt Designer allow me to create some kind of prototype, but it's a little to close to code.

I heard somewhere about Azure, but I'm not convinced it would be useful in Game Design.

Yes, pencil and paper are always with me - but later on it will have to be transfered to digital form.