This post might need to be moved to a different place. I wasn't sure where to post it, but others might find this useful.
It took me a few hours to figure out what was going on with omeka when i first put it behind a reverse proxy. the links that get generated inside the html wasn't what I expected. Anyway, if anyone ever wants to get omeka (0.10b) (or the okapi package) working behind a reverse proxy below is a cut and paste of what have in my apache config...
#
# omeka and okapi test installs
#
#ProxyHTMLLogVerbose On
#LogLevel Debug
ProxyRequests off
ProxyPass /omeka http://myvirtualmachine.mydomain/omeka
ProxyHTMLURLMap http://myvirtualmachine.mydomain/omeka /omeka
ProxyPass /okapi http://myvirtualmachine.mydomain/okapi
ProxyHTMLURLMap http://myvirtualmachine.mydomain/okapi /okapi
ProxyHTMLLogVerbose On
<location /omeka>
SetOutputFilter proxy-html
ProxyPassReverse http://myvirtualmachine.mydomain/omeka
ProxyHTMLURLMap /omeka/ /omeka/
ProxyHTMLURLMap /omeka /omeka
</location>
<location /okapi>
SetOutputFilter DEFLATE;proxy-html;INFLATE
ProxyPassReverse http://myvirtualmachine.mydomain/okapi
ProxyHTMLURLMap /okapi/ /okapi/
ProxyHTMLURLMap /okapi /okapi
</location>
with the above i now get http://www.mydomain/omeka
and http://www.mydomain/okapi instead of having the http://myvirutalmachine.mydomain/ baseurl.
you will need the mod_proxy and mod_proxy_html modules for apache enabled for the above to work. Also I had to disable zlib compression for the okapi package (0.9.2). I have tested it extensively yet, but it appears to work.