What anonymous FTP servers are being indexed?
We are currently, and slowly, building a database containing not only FTP hosts, but also dynamically indexing all the files on these hosts.

It does take a bit of time for the medium-sized hosts, where smaller are somewhat faster.
While our custom-built crawler can handle ls-lR indexes, we have found many to be either slightly broken and or mangled, which means we have to rely on traversing all the directories.

Currently Available
ftp.rfc-editor.org,
ftp.aminet.net,
ftp.apple.asimov.net

Currently In Queue
ftpmirror.your.org,
hobbes.vespernet.net,
ftp.sunet.se,
ftp.lysator.liu.se,
ftp.icm.edu.pl,
ftp.belnet.be,
ftp.mirrorservice.org