I want to build a program that will (as part of what it's doing) display lines organically growing and interacting horizontally across the screen. Here's a sample image, just imagine the lines sprouting from the left and growing to the right:

The lines would look like the lines used on Google Maps Transit Overlay or OnNYTurf's transit pages.

It's a personal project, so I'm open to just about any language and library combination. But I don't know where to start. What have you used in the past to create graphics that are similar to this? What would you recommend? I want it to run on Windows without any extras needed (.Net is fine), and it doesn't have to run elsewhere. I needs to run as an actual program, not javascript in the browser.

There's obviously no 'right' answer to this, but the purpose isn't to start an argument about X better than Y but rather just find a list of graphics toolkits that do simple 2D graphics that people recommend because of their ease of use or community or whatever.