Back in the 80s, most home computers used to boot into a dialect of BASIC. This made it very obvious how to start to learn to program - just type things in and try things out to see what works.
Modern computers are much richer in many ways but do have the disadvantage that it's less obvious how to start programming. One could even be forgiven for assuming that the typical off-the-shelf Windows Vista machine doesn't even come with a built in programming language. Actually there are 3 (at least) - the windows command shell language, VBScript and JScript (JavaScript). The windows command shell language (the descendent of the MS-DOS batch language) is ugly, badly documented and almost impossible to debug so lets skip that one. Between VBScript and JScript, the latter is better to learn because it's cross-platform and VBScript is Windows only. There are two ways (at least) to run JScript in Windows - one is through the Windows Script Host (wscript.exe or cscript.exe) and the other is through the web browser. The latter is a graphically rich, interactive and familiar environment so I think that's the way to go.
JavaScript is a much nicer language than the 8-bit BASIC dialects from the 80s but it's still not very discoverable. The tutorials and reference guides are all out there but you have to have a text editor open in one window, one browser window for your program and at least one other browser window as containing your reading material. I think that this is a problem that could be solved with a website.
I'd like to see a site which does for Javascript what computers booting into a BASIC interpreter did for BASIC - a one-stop shop for (at least beginner-level) Javascript development. It would allow you to type Javascript code right into a web page and see its output right there on the page immediately (perhaps with separate divs within the page for the Javascript code, the program's output and tutorials).
The code editor might have syntax highlighting, intellisense, a built-in debugger - whatever can be provided to make programs as easy as possible to develop.
Once you've written some code you can save it on the website and access it from anywhere. You can also share it with friends. If one person defines an object someone else can use that object in their programs. In this way, a rich ecosystem of scripts can develop.
Another possible refinement would be for the web server itself to provide some abilities that scripts can use. Perhaps just storing a small amount of data per script per user so that scripts can do some persistent stuff, or perhaps allowing some server-side JavaScript as well as the client-side scripts, to enable the writing of rich AJAX web applications.