I think the main problem with your site's design is not so much with graphic design as with user-interface design. Specifically, when I look at your screenshots above, the question I ask myself is not "Cool, what should I try first?" but "What the heck is this, and what am I supposed to do with it?"
This is a common issue with websites and other user interfaces designed by engineers (or other domain experts): they already know how the system is supposed to be used, so to them, everything's fine as long as all the features they need are conveniently accessible. Alas, this often leads to all the features being equally conspicuous and accessible, giving the new user very little clues on where to start.
Graphic design does have some effect here, insofar as bad graphic design can make any user interface confusing, whereas good graphics can enhance the user interface by making the meaning and relationships of different interface elements clear and drawing the user's eye to the most important elements. But fundamentally, the problem is more about what to present to the user and how to structure it than about how to make it look nice.
OK, let's get a bit more specific. My first piece of advice would be: simplify! You might want to take inspiration from Google's original front page design, which basically had three elements: the logo, the search box and two buttons (and one might argue that the second button was unnecessary clutter). Oh, and a few links to other pages with more stuff — which were clearly marked as being of secondary importance by being lower down, in a small font, and/or in gray — and a copyright notice, apparently added as a subtle hint to users that the page really did end there.
Or take a look at Doodle, another company with a noodly name and a simple but effective front page design. For convenience, I took a screenshot of their front page and added some red scribbles on top:
Doodle is a pretty good site to compare yours with, since their site, like yours, is basically a framework for allowing users to design their own content (quizzes for you, event schedules for them) and invite other users to interact with it. The big difference is that, unlike your design, the Doodle folks spend a lot of effort easing their users gently into the interface, instead of just tossing them into the deep end of the pool and waiting for them to sink or swim.
Looking at their front page, especially without my scribbles, the obvious thing about it is how little stuff — especially irrelevant stuff — there is on it. Sure, there's a whole bunch of little notes and links at the bottom of the page, but that's all "below the fold" and something new users will just ignore. The second most visible thing, in big friendly letters right where the user is likely to look first, is an eight(!) word blurb explaining what the site is about. The most visible thing is the big graphic showing, in simple pictures, the main steps of the workflow, making it all look easy and inviting. And right between them is a big button inviting the user to click it and get started.
In fact, in the top part of the page, there are only four clickable things (excluding the logo, which is clickable — as users expect it to be — but just takes you back to the front page): two links to the first step in the event scheduling wizard, one to a canned example for users not confident enough to jump right in, and one unobtrusive link in the upper right corner that opens a pop-up login dialog for established users. That's all.
So what about your site as it is? The first thing in your screenshot that jumps out for me as something that might possibly be worth looking at are the green headings, which at least are short, in large type and in the middle of what looks like the "content area". Alas, there's nothing much of interest there — the "Topic Information" section just has some trivial metadata that should be in small print in some corner, the "Sub Topics" section has a couple of links (to other similar pages?) which appear to duplicate those in the top right corner, and the "Resources" section is simply empty. And besides, even after reading all that, I still have no idea what the site is about or what I can do with it.
So, what can I do with your site? Well, you say that I can create and take quizzes, so how about putting some big and attractive-looking links/buttons on the front page that say "Take a quiz" and "Create a quiz"? (The former should be more prominent, since a new user is presumably more likely to take a quiz than to create one, but including the second one on the front page at least lets users know that they can do that too.) Also, a short explanation — from a few words up to a short paragraph — of what your site is about would be good too. (That could also be a good place to tack a "read more" link onto.)
There's a bunch of other things you could lose too: for example, as a new and unregistered user, why am I seeing what looks like a "delete" link? Can I really delete the page? If yes, why? If not, why is the link there?
Similarly, the "(703 Available questions)" note is a pointless distraction where it is, as it looks like an interface element. If you want to impress visitors with the depth of your site, put that where it belongs: in a suitable impressive looking blurb in the content area. ("We already have 703 questions available, and more are coming!")
Finally, I should note that everything is relative. TV Tropes, for example, has a horrible user interface (much like yours, really), but it doesn't matter, because they make up for it with loads and loads of excellent and densely interlinked content, so that most new users won't have to touch the navigation interface at all. Actually, that's pretty common with wiki sites; Wikipedia isn't really that much better. The catch, however, is that you need to already have that load of content (or a user base committed to creating it) before that effect can start working for you.