A few years ago, there were websites that would estimate readership of
usenet newsgroups. Does anyone have current data on which usenet
newsgroups have the highest readership, highest post count, and
highest in disk volume?

Dear twiddler,

NewsAdmin.com publishes a number of reports providing statistical data
of the kind you are looking for. Please follow these links to view the
most up-to-date figures (currently as of Sept. 8, 2002):

Top-100 Newsgroups by Readership:
http://www.newsadmin.com/top100reads.htm

Top-100 Newsgroups by Number of Postings:
http://www.newsadmin.com/top100msgs.htm

Top-100 Newsgroups by Bytes posted:
http://www.newsadmin.com/top100bytes.htm

Top-500 Newsgroups by Swings and Changes in Message Activity:
http://www.newsadmin.com/byteschng.htm

Chart: Average File Size of Articles being posted to Usenet by day and
month:
http://www.newsadmin.com/cgi-bin/msgsummary

Source:

NewsAdmin.com: Usenet Statistics, by PathLink Technology Corp, 2002
http://newsadmin.com/spamreports.htm

Search terms used:
"usenet statistics":
://www.google.de/search?q=%22usenet+statistics%22&ie=UTF-8&oe=UTF-8&hl=de&meta=

Hope this is what you were looking for!
Regards,
Scriptor

this was exactly what I wanted. Thank you