I use Textmate with Terminal. There's an bundle for it here -> http://github.com/aran/arc.tmbundle It's a little out of date, but you can easily hack changes to it if you need to.

> What does Arc have built in? Is it ALL covered in the tutorial?

Arc has nothing built in (for ide/gui/editor management), so it's not covered in the tutorial.

> Why isn't there a little website that lists and documents all the built-ins in Arc?

I think pg (paul graham) has chosen this forum as a means for distribution/collaboration. I suggest you check into -> http://af.searchyc.com/ since, by default, the forum has no built in search mechanism There's also google -> http://lmgtfy.com/?q=arc+forum+between (lol - I had to use lmgtfy at least once in my life :).