Rob Chartier is excited about discovering the Subversion script hooks.
I wrote a post-commit hook program in C# for our subversion server that generates a detailed commit notification email using the svnlog command. The program then uses a config file to determine which users get the message depending on the name of the repository. It was very easy to do and hasn't caused any problems in the two-months and 350+ commits that we've been using it. Knock on wood...
The "script hook" system is a great way to integrate disparate systems. It is used extensively and ingeniously in Qmail, a super-fast and extremely stable and secure mail transport system for Unix. Qmail's script hooks make it very easy to automate almost any process when emails are sent, received or queued. It also helps reduce code bloat and memory usage by separating steps into small programs. For example, compare the amount of bugs and security vulnerabilities in Qmail with those in Sendmail or Exchange Server. Qmail has almost none, while the other two have more than I could ever read.