This is a free tool from Microsoft that I have found really useful of late: Log Parser. Log Parser allows you to specify a myriad of input formats including:

• the registry,
  
• local filesystem,
• event logs,
• delimited text files,
• free form text files,
• IIS logs (all formats),
• XML files,
• and Active Directory!

and then run SQL commands against the input files as if they were a database table, outputting the data to another myriad of output formats including:

• XML files,
• delimited text files,
• STDOUT,
• ODBC Compliant database files,
• and Syslog

One command line of easy to understand syntax (if you know SQL) can convert XML to a csv file with data conversion along the way. Extremely handy against Event logs (failed login attempts), IIS and firewall logs.