FontStruct offers a free, web-based font construction environment (with a grid and primitives) that outputs TrueType fonts to use on either Windows or Mac. There's also a gallery for sharing fonts created on the site.

Not high end, but probably a useful space for experimenting and teaching about type. (As you can probably tell, I haven't actually used it, but it's on that long, long list of Things I'll Work On After the Semester is Over, I Mean It This Time. Also, there's the fact that the userid and password I registered on the site aren't working yet.)