Hi...great site. Lots of elements I like. Not that into the colors in the lettering. More importantly,I would agree that it's a bit difficult to know where to begin when you first get to the site. I believe that's becuase it seems like the rounded corner box titled ThemeBot.com has the Home link in it. All three of those links could be in the blue global nav bar across the top. In a sense it's like there are two global navs as it stands now. My suggestions would be to incorporate those three elements into the global nav, and remove that box. The next one under it, New Themes, is very self-explanitory and obvious. (It should be on the gallery page as well, but it's currently not.) You could bump the New Themes box up, to replace the ThemeBot.com box, or fill the space with something that doesn't look anything like a navigation cue.

I would suggest that the member log in be at the top on the right side (that's where they are often found), or in the very top right corner where the beveled search feature is, but that would leave only New Themes and News on the right. So...since I don't personally enjoy three column layout (I feel it squishes the centre content too much and makes the whole site feel crowded and chaotic), my more severe suggestion would be to eliminate the left column. The progress report in the centre isn't a real head-turner for looks, so maybe consider putting a short sentence about what the site is for, followed by the new themes with a few screen shots for appealing visuals and as an aid for the viewer to see immediately what the site is about. The 'news' element currently appears twice, and even if they aren't the same, there should only be one 'news' section.

Eliminating the left column would allow a lot more freedom in the main viewing area for screenshots of new themes, or "most popular" or whatever, but more importantly, it would leave a single dominant global nav. to guide people into the site. It's more important that a table of contents, and its an immediate indication of how easy the site will be to navigate.

I do like it though. I like the background rectangles with sublte lines and drop shadows, I like the green, would have to strongly agree with MamaLoca's advice. Stick to one type of color, earth tones or primarys or something...check this out : kuler.adobe.com/ I'd stick with colors similar in value to the green on the tabs. Nice work all in all!

That's good to know-
Again, putting on my IA hat I would suggest that you take a little time and write down those different roles you just mentioned and a little bit about what they might need on your site.
For example:
> professional web designers: probably want to see themes listed by platform/cms or by type (business, portfolio, non-profit, etc.), a place to list their services, upload their logo, etc.
> template creators: how do they upload and promote their templates?
> developer: where do I tell you that I work with drupal and can customize any template you buy?

so, thinking about what these different visitors want to do will help you then determine the types of links you need to guide them to the conversion point (from being just a casual visitor to being a contributor/downloader/advertiser/etc.).

Good luck!