I, too, like Carl's designs, but I have slight doubts about the style of the "Search" button. Basically, with buttons disguised as images, I never know whether the site designer expects me to initiate the search by clicking the image or hitting return. So I'll hit return, then click the button if nothing happens.
I know it ain't pretty, but I prefer to see web form buttons in the default style -- it's just so much more consistent with the rest of the web look and feel (ditto for blue underlined hyperlinks). These default buttons also have the nice property that they highlight when the user tabs onto them.
As a final comment, the translucent pill style feels like a "me-too" homage to Apple's Aqua.
To me, the overall page looks nice and "lightweight": not too much noise, nice whitespace, and it should feel snappy as well. At this point I should confess that I almost never visit the OpenACS.org homepage because it's just too static. And the font's too big so the information density is lower than I like. Any of the designs shown in this thread will be just fine if these more fundamental flaws are corrected.
