Having downgraded to Splunk Free, I can no longer see options when scheduling a search to configure summary indexing. That's despite http://docs.splunk.com/Documentation/Splunk/6.0.2/Admin/MoreaboutSplunkFree which says that when switching to Splunk Free "Any alerts you have defined will no longer fire/function, although you can still schedule searches to run for dashboards and summary indexing purposes."
I've upgraded to Splunk 6 but I still can't see the summary indexing options.
I believe that is the line about report acceleration summarization in v6. Try looking up tscollect and try adapting your searches to use that at the end of the search command. You can see if you can use that to collect your own results into an index and they work with that summarized data.