I am a moderator of a few yahoo groups.  I do not want these pages to
be cached.  In other words, I do not want them to be entered into the
google index.  How do I remove them?  Thanks.

I don't know if you'd like to hear a negative answer, but in order to
prevent the indexing of the webpages, you'd have to move your business
elsewhere. Yahoo! does not allow you to control the script and insert
a command preventing the Google bot from indexing these pages. If you
had your discussion group on your own page, it would have been very
easy: just insert this command, and you'd be gone from Google.

Making your page title as blank(no title) wiil do so. or atleast i think so

may be, try moving some pages(dont want index) to free web hosts, and
make a link from your host to this host..

110mb.com, the best ever free host, no ads, 1000mb, asp,php,mysql support!!!

You may want to check out if you can use a robots.txt file in the main
directory of your group, that can stop part or all of it being indexed. 
Check out specifics at

http://en.wikipedia.org/wiki/Robots.txt

This tells automatic web crawlers to skip some pages, or the whole directory. 
Google respects this file. Yahoo does too, and their stuff may also be able 
to help you with it. This involves no script changes, (just adding this one
file that only bots see) and may be acceptable to Yahoo.