Front Page With Categories Only?

Is there any free template or way to easily manipulate a current template so that the ‘front page’ of my wordpress blog would only have the Categories? I’m interested in giving visitors a choice of what categories they want to read prior to them seeing any messages (as opposed to them seeing whatever messages have been posted lately and then simply seeing a sidebar option for selecting various categories).

Thanks in advance. Oh, I should mention, this is all very new to me and I am not exactly what you would call an expert at editing code.