I'm a translator. I'm looking for some kind of web app to create a
system where my customers could log in and see their active projects
and its status, along with other interesting information, letting them
to download a final file when the project
has been finished.

I look either for a specific tool to do it, or a more open tool
customisable for my purposes.

I've been trying with some combination of mambo/php-nuke + plugin, or
osCommerce without success.

I have experience with html, asp, php and web technologies in general.

Thank you.