I've installed non-Market apps on my AT&T Captivate using adb, but it'd be nice if I could download an APK directly and install it locally. I've heard of "App(s) Installer" and about a hundred variations on similar names, but it looked like those were just intended to work on devices with a working package installer (e.g. not one that's had the ability to run unsigned apps stripped out).
I've rooted the phone -- is there some way I can either replace the existing package installer with one from e.g. another Galaxy S phone on another carrier, or maybe just an app that asks superuser permission before installing the APK itself? Is this something I could just do directly from (su'd) terminal on the phone? I'm sure somebody has thought of this already but I'm having trouble finding an answer on the web... maybe I just don't know exactly how to ask.
ETA: please note that this is original AT&T firmware. The carrier is blocking non-market app installs, I think by modifying the package installer. I'm aware of the setting to enable unsigned apps, but on my phone it has no effect.