I tried this.

Before I started, DiskUsage reported 86232 KB available in /.
I believe that to be the root of the drive where apps live.

I installed Rhapsody and uninstalled it without running it.
DiskUsage reported 83916 KB available.
I rebooted.
DiskUsage reported 86100 KB available.
I installed Gizmo and uninstalled it without running it.
DiskUsage reported 84004 KB available.
Reboot.
DiskUsage reported 84108 KB available.
The useless icons are gone, but it looks to me like I actually lost 2 megs out of 256.
I'm going to reflash pretty soon anyway, which is why I'm experimenting now,
but next time I'm going to find where the installer lives and delete it directly.
Installing and uninstalling is bound to leave some residue,
and could very well screw things up by altering libs.

BTW, if I'm looking at the wrong numbers,
please let me know. I'm very new at this.