VirtualDub is more of a
video processing
program than an editing program. This is supported by a
quote from the VirtualDub
website:
There are lots of programs that let you "edit" video. And yet, they're frustratingly complex for some of the simplest tasks. VirtualDub isn't an editor application; it's a pre- and post-processor that works as a valuable companion to one.
http://www.virtualdub.org/features/
VirtualDub has some of the same features as many video editing applications, such as video capture support and rudimentary linear cut & paste editing. However, VirtualDub was never intended to be a nonlinear editing application, so it's really unfair to compare it to software such as Adobe Premiere or Pinnacle Studio.
As a video processor, VirtualDub is untouched by any other program I've used. It comes with a set of optimized video filters for resizing, sharpening, deinterlacing, cropping, etc. and you can write your own filters to enable it to perform an unlimited number of video processing tasks. Basically, anything you can feasibly do to video (and, to a large extent, audio) can be done with VirtualDub. In addition, it has real-time previewing of output and is extremely optimized, which is good for those of us with little patience.
VirtualDub is open source software and is distributed under the GPL. You can download binaries and source code (Windows-only) from http://www.virtualdub.org/.