So far I've got the overworld map in, and the player character (Link) can move from screen to screen (albeit without being constrained by things like mountains and oceans, because I haven't implemented collision detection yet!) Keyboard support is in, but there's also a set of buttons duplicating the NES controller which you can use as well: The Legend of Canvassa (yeah, I know, stupid name... =P)
Since this uses the <canvas> tag from HTML 5, it currently only runs in Firefox 2+, Webkit and Opera 9; IE users are out of luck. (Yes, I know there are hacks that enable IE to emulate Canvas... but so far I haven't been able to make them work with my code). I've successfully tested it in Firefox 3 and Chrome, so in theory at least it should work in Safari (Chrome and Safari are both Webkit-based, after all). Opera I don't know.
Anyway, this is only Part 1 of what could potentially be a lengthy project, and I suspect I'll continue to scratch this itch over the coming weeks, so look for more updates as they come.