Visualization & Design
Visualization of understanding is much more important than merely making it look "good." The visualization is integral to the communication as it is the organization made visible. Often, data and organization (and thus understanding) gets concealed when the type of visualization doesn't match the organization or the goals of the communication, or so highly distorts it that it is difficult to see.
Good visualizations pay special attention to scale (relative or absolute), orientation, view, projects (especially in the case of maps), detail, generalization, and layers. Some effective diagrams can use not only representations of three dimensions to represent three aspects of the data, but use color-coding and/or symbols to introduce from 1-6 more dimensions into the chart.
Interface design is another aspect of the visualization of the design of experiences. Over the years it has expanded a bit to include not only software applications (programs), but kiosk and CD-ROM interfaces as well. To some extent, website interfaces have been embraced by the general interface community, but interface designers have resisted the expansion of the term to include print-based interfaces and other non-digital experiences, even though most of the approaches serve experience design in a greater sense.
You can think of interface design as encompassing information design, interaction design, and some forms of sensorial design (mostly visual and auditory design, since most computers can only display sights and sounds). Typically interface designers have addressed the layout of screens, the design of screen elements like icons, and the flow between them.
There is a wealth of design knowledge and innovation within the interface design community and most of it is not published on the Web. Many of the online industry's so-called innovations were already pioneered and developed with the interface community, and usually researched much better than the solutions created in the last few years.
While visual design has, traditionally, been concerned with appearance, it can communicate more than mere beauty, but meaning in any decision that builds that appearance. In particular, graphic and illustrative styles convey cultural cues that help designs be identified with different values. Though most designers make choices based on what they prefer or what "looks nice" and, unfortunately, are taught to, the best designers choose each element of visual design, including typography, color, layout, and photography based on how they communicate the goals and the message to the intended audience. The overall design must still feel consistent and clear, and it should certainly be handsome, but great designs communicate first and are beautiful second instead of the other way around. Likewise, these designs tend to transcend trends more readily since they are build upon a more meaningful and less stylish foundation.
Style is a difficult thing to categorize or characterize because different elements communicate different meanings to different people. Few people have a well-educated understanding of design or a high visual literacy. However, this isn't their fault as much as it's merely a missed opportunity in our society. This makes it more challenging for designers to construct experience but as long as their focus is on their audiences and not themselves, they can communicate more successfully.