Larry,
 
I don't know of a way to clear the cache. I tried lowering the time to display in settings but it made very little difference.  The large number of guests is usually due to search engine traffic unless you are a very popular site. You can verify this by looking at the server log.
 
One month Google searched my site a lot generating 9.5gb (not a typo - gigabytes) of traffic by themselves! I asked them why so much traffic, got a reply about sending them the IP they were searching from.  I never got around to sending that info back as the server log was so huge I couldn't find it!  Not too long after that (a month or so) it went back to normal levels of activity from them (350mb or so).
 
I think the problem I had was the Google sitemap module.  The one I had at the high traffic time was a very early version maybe even the first one released. The newest one seems to do much better at giving them the sitemap.
 
That's my experience.

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On 10/17/05, Larry <naasei@gmail.com> wrote:
How do I clear cache of guests online?
 
Eg I have 
 
"There are currently 9 users and 504 guests online."
 
I wish these 504 guests will join us online :)
 
Larry Osei-Kwaku