Statistics and log analyzers
These are tools to analyze SpamAssassin logs and generate reports. Generally, they take syslog data logged by the 'spamd' server as input.
mailwatch -- no demo, but the previous link has screenshots
sa-stats for 3.3 Not updated since 3.0 (or earlier) This works OK for 3.2.5, but you might benefit by changing the default log file location, and start time (try "yesterday"). --top=10 seems to produce unlimited output. The script doesn't seem to analyse usefulness of particular rules, but the performance figures might be helpful.
munin: Munin is a tool for graphing all sorts of information about one or more servers and displaying it in a web interface. It uses the excellent RRDTool (written by Tobi Oetiker) and is written in Perl. demo available
PostConf -- Postfix and SA management and content analysis (free and commercial)
sa-stats.pl (Dallas Engelken's version) : Generates a report in text or HTML from a spamd log file or from syslog. not to be confused with the "sa-stats.pl" in the SpamAssassin distribution; it's entirely different. Rules Emporium is no longer available. There's a copy of version 0.93 available here
sa-exim-stats : Generates rrdtool graphs from sa-exim log files.
spamdstats: Continuously parses spamd's log file in the background and stores various data in one Berkely DB file to be read by a second script.
sa-daily-report: Generates and mails a report of all the email quarantined as spam the previous day, to allow checking for false positives.
If you plan to parse spamd's syslog output, some helpful notes can be found at SpamdSyslogFormat.