When I first started evaluating CMS/site frameworks, one of the things that I really enjoyed was a site gallery. I missed that here, but fortunately that didn’t keep me from seeing what a jewel MODx is.
For instance, with some CMS’s, you can tell from their gallery that the CMS is going to lock you into one layout, orientation, or convention. Others may show a greater diversity in site structures and layouts and therefore more promise to the inexperienced developer. Some may show a complete disregard for CSS and XHTML standards, using tables and hacks, while others (like MODx) leave that up to the designer, which will always yield some fantastic results.
I think that more advanced web developers can look strictly at descriptions and documentation and understand what the CMS is capable of and what its limitations are, but for the beginner web developers transitioning to intermediate, I think a site gallery goes a long way in showing its potential. It also helps us "visual" learners.
Perhaps a locked forum that only moderators can access, with each new post being a site in the gallery? That seems like it would be easy to maintain, current users could subscribe, and you link to it from the site’s main content. I understand we have a "You and Your Sites" forum, but that seems to be geared more towards the current-user crowd than the overwhelmed n00b surfing the web for a CMS.