I'll give you the info, but that story vaguely rings a bell, and I think it might be a bug (e.g. it might just not be displaying them). If you have the rootsh package installed, then try this first: close App Manager, open up X Terminal, and type:
root
and then:
apt-get update
and then try App Manager again.
I'll post the repo info momentarily

UPDATE: Here they are:
1)
Name: Nokia Applications
Address: https://downloads.maemo.nokia.com/fremantle/apps
Distribution: ./

2)
Name: Nokia System Software Updates
Address: https://downloads.maemo.nokia.com/fremantle/002
Distribution: ./