Free tools for assisting with designing a game (graphs, logical process, etc.)

Hey all,

I'm putting together my toughest, most challenging game so far. And one of the challenges that I've set myself is to be more organised and 'professional' as ever.

So far I've been putting together a basic Game Design Doc together whilst prototyping some "under the hood" stuff. But now that I've got the ideas for the core mechanics done I want to start designing how it's all to go together.

So, apart from an Office Suite (I'm using OpenOffice) and a doodling program (GIMP) what else can I use to put together the design of the code, logical process of the code, player interactions?

Also, any good resources for relative beginners for putting together the design aspect of the game? Overall architecture of code, UI, etc?

I hope this isn't too vague, but I'm teaching myself. And the biggest thing I've learned so far is that I know nothing XD hence the questions.

So on I've been ploughing on with only my ideas on whats sensible... but then having to come back here and ask questions.

Many thanks for reading this, I'd appreciate any help you could give.

Mike