Time. Software is increasingly focussed on helping us understand and manage it. For a great example, see the unreleased Palm Pre; it's diary view shows spare time in a beautifully simple 'crumpled' concertina UI. So, how do other UIs handle time?
Lukas Mathis' blog, ignore the code, recently covered some mockups of current, and possible temporal interfaces. Including one from this blog :-) One of the examples showed how the file 'list view' could better serve temporal thinking.
Lukas' approach inspired some thoughts of my own on the problem of representing time visully. I've put Lukas' original example topmost with my iterations below; if an item is separated in time from the other items — and since we seem to think about time in a spatial way, how could we show this spatially? (click for fullsize)
I like the 3rd, 'peaks' iteration as it reminds me of something I saw in Norway — a 'Give Way' line evoking a steep slope, big bear teeth, or sharp spikes. "Slow Down!" It seems a nice visual metaphor for time.
How else could time be shown spatially in this context?
Another conversation for another day: missing UI metaphors for working with (as opposed to simply understanding) elements which travel through time. We can tell it's a problem because people are going to the effort of devising complex workarounds. For example, the 37signals crowd has a nifty solution for throwing emails forward in time.