Ok, everyone who’s been doing this for the past two years can laugh at me for taking this long to figure it out. But if you’re slow like me, you look for new apps for your n8xx on your PC, where the browser is fast and the screen is big. Then you navigate to the same place with the browser on your gizmo so that you can push the little “Install Now” arrow icon and start the application manager downloading and installing all the files you need.
Or click on that same icon in your PC browser, save the contents of the incoming whatever.install to your disk, and send it to your n8xx by bluetooth connection, and watch it open automatically with the application manager. Whee. I should have thought of that the first time I saw a .install file: maemo is *nix, so once you hand the application manager the right file, it couldn’t care less what route it traveled. (Yeah, if I were really cool I’d write a firefox plugin that invoked the transfer automagically. No security issues there.)