Pherhaps they are scripts from spammers looking for open proxies. My assumption is that they look for available (and misconfigured) mod_proxy modules. There is nothing wrong with this, but what puzzles me is that the server is logging a 200 (success) and shows a high byte count returned to the client.
I almost freaked out, but then I realized that the server always returns my local index page to the client, no matter what the CONNECT request is. I verified this by issuing a CONNECT manually, no matter what I request, I always get a 200 and the contents of my webpage, as I would with the regular GET method.
It isn't terribly bad as I know for sure mod_proxy is not working. However, it would be kind of nice if I saw a "403 Method not Allowed" instead of the scary "200". At least it will prevent my server form being wrongfully listed in some spammer's list.
This seems to be a bug that only takes place on systems with php installed. For now I have <limit>ed the CONNECT method. It does not address the issue, but at least they show them a "404 Forbidden" instead of a "200" message. If you see this, simply add the following lines to your httpd.conf file and restart apache:
<Location />
<Limit CONNECT>
Order deny,allow
Deny from all
</Limit>
</Location>
<Limit CONNECT>
Order deny,allow
Deny from all
</Limit>
</Location>