Are you sure you wanna do blue against white? That color scheme is sinfully generic. I think it's waaaay over used and a bit heartless. But there must be a reason why nearly every HUGE corporation goes with that particular scheme.
Well, i'm sorry to say, i don't really think this is a right step. First of all, what do you want to communicate? What is your audience / target, what is the purpose of the poster, where will it be displayed, what size will it be, how long do you intend to use it and so forth.
I like the tag clouds but i'm trying to understand why they form a circle / sphere. Is there a particular meaning to it? What is it trying to say? Apart from that, i think tag clouds that highlight particular features, like what you've done here, are better off using a single font, or perhaps 2 at tops.