NewSyslog is an updated version of a package put together by Theodore Tso of MIT Project Athena (which is included in NetBSD, FreeBSD, OpenBSD, etc.). It manages the rotation and archiving of log files (primarily those written to by syslogd). This version has a mix of features from all of the other versions, and it has been made more portable than any of the others with the help of GNU Autoconf.
pflogsumm.pl is designed to provide an over-view of postfix activity, with just enough detail to give the administrator a "heads up" for potential trouble spots. Reports includes: Total number of messages and bytes; Hosts/Domains; senders and Recipients; per-hour traffic reports; summaries of warnings, fatal errors, and panics; and so on ...
ScanErrLog is a Python module that allows you to parse Apache error_log files and present their data in decreasing order of occurences of error messages. This is particularly useful if you want to quickly solve the most annoying problems Web visitors encounter on your site. You can use it directly from the command line, import it into another Python program and use the classes it defines, or use it as a CGI script. You can produce reports in HTML, PDF, XML, or Plain Text formats.