Most mirrors should be still up, where they were ever up before (a lot of mirroring services have been shutting down lately which is sad).
What is unfortunate is if the DNS for aminet.net domain was hosted at WUarchive.. if so all the nice URLs for the mirrors will drop off the planet eventually but not because of failure.
I would basically prompt whoever looks after Aminet now to reorganise and reconfirm all the mirrors and pick one to act as the master. No doubt this would end up being the Paderborn mirror..
http://ftp.uni-paderborn.de/aminet/
