ResExcellence is the Mecca of Mac GUI customization. If you're into changing the look and feel of your Mac, you more than likely hang out at ResExcellence. ResExcellence, in terms of content, is decent, and it has assloads of desktop pictures, icons, application makeovers, and other stuff of that nature. ResExcellence is your one-stop shop for pimping out your Mac, but it is pretty disorganized, so don't expect to be in and out in a matter of seconds.
We'll start out with the universal layout. As is true of most sites, the title is in big print at the top of the page (so you'll never forget where you are ;) ). Right below the title is a big box with links to all the major sections of the site. After that is the main section. On the left, there is a column with links. Unfortunately, it tends to be pretty inconsistent. The layout is decent (although drab looking), but needs a bit work on organization.
The homepage crams a lot of information into one page. Often, having too much stuff on one page can make it a bitch to find what you're looking for. However, unlike other aspects of ResExcellence, the main page is fairly well organized. Even though the various topics are in a fairly random order, which seems to change with each update, the topics are labeled clearly enough that this isn't a huge problem. One thing that bugs me to no end is that the left sidebar on the main page is different than that of other pages. Almost all the pages have a link to the Mac OS Classic mods, but only the homepage has links to the interviews. And the list of classic mods seems to vary from page to page. Also, the home page is one of the few pages that doesn't say where to go to report a broken link. This seems a bit odd.
Where ResExcellence truly shines is in the area of downloads, namely GUI modifications. It has hundreds of Mac OS X themes, Shapeshifter guiKits, icon sets, desktop pictures, iTunes skins and mods for basically every Mac app. However, these are all files one could find on a variety of other sites. What makes ResExcellence so great is that it brings all this stuff together onto one site. I can just go to ResExcellence to grab that shapeshifter kit or whatever I'm looking for, rather than having to hunt and peck through the myriad of websites. This is a really nice feature, especially since I happen to loathe internet search engines.
One thing I happen to like quite a bit is the "Desktop Snapshots" section. If you're as lame as I am, and your favorite webboard thread is "Show us your Desktop," you will be in heaven. This is just an archive of screenshots people have taken of their desktops. If you search around a bit, you will see my old desktop when I was still running classic.
Overall, ResExcellence is a nice site. Where it falls is in the area of organization. As far as organization, the site seems very much thrown together. Yes, there's a shitload of information, but you will find yourself needing to use the forward and back buttons. As a former web designer, I know that this is really bad form. So set of 30 minutes or so and screw around with your GUI. You'll find everything you need at ResExcellence. But don't expect to find it too quickly.