plotting large datasets

[DJ Delorie]

I've got a need to plot "value vs time" data for 32 channels
simultaneously.  Gnuplot isn't up to the task (not enough uniqueness,
even mixing lines and points, or control - the graph is just a mess).
What else is there?

Ideally, I'd like something I can interact with - enable/disable
channels, highlight channels, change the time range, etc.  The data
comes from processed log files, so either file or API input is OK.

Ideas?