I've always found checkin (commit) mails to be very useful for keeping track of what work other people are doing in the codebase / repository. How do I set up SVN to email a distribution list on each commit?
I'm running clients on Windows and the Apache Subversion server on Linux. The answers below for various platforms will likely be useful to other people though.
You use the post-commit hooks. Here's a guide.
Here's a sample Ruby script that sends an email after each commit: commit-email.rb
Have a look at the standalone Subversion Notify tool (Windows only!) It can do emailing on commit and also much more!
What platform?
On Mac OS X I have installed msmtp and created a post-commit script under hooks in the repository. A .msmtprc file needs to be setup for the svn (or www) user.
REPOS="`echo $1 | sed 's/\/{root of repository}//g'` "
REV="$2"
MSG=`/usr/local/bin/svn log -v -r HEAD https://localhost$REPOS`
/usr/local/bin/msmtp {list of recipients} <<EOF
Subject: SVN-Commit $REPOS#$REV
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8Bit
$MSG
EOF
Make {root of repository} and {list of recipients} specific for your needs. Note I have used UTF-8 because we have some special characters here in Sweden (åäö).
There's a related question here on post-commit hooks. Personally, I prefer to send a message to something I can get an RSS feed from, as an email-per-commit would overload my inbox pretty quickly.
Seconding @Matt Miller on RSS feeds.
There's a useful tool called WebSVN that offers RSS feeds of every repository and individual branches/tags/folders with full commit messages. It's also a great web interface for quickly looking at file histories and commits/diffs without having to run an update and open your editor of choice.
As someone else said, 'what platform'. On Windows I've used 'blat', which is a freebie command line SMTP mailer to do this, along with a post-commit and another batch file.
The post commit looks like this: (Just calls another batch file)
call d:\subversion\repos\rts\hooks\mail %1 %2
And mail.bat looked like this:
copy d:\subversion\repos\RTS\hooks\Commitmsg.txt %temp%\commit.txt
copy d:\subversion\repos\RTS\hooks\subjbase.txt %temp%\subject.txt
svnlook info -r %2 %1 >> %temp%\commit.txt
echo Revision %2 >> %temp%\commit.txt
svnlook changed -r %2 %1 >> %temp%\commit.txt
svnlook author -r %2 %1 >> %temp%\subject.txt
c:\utils\blat %temp%\commit.txt -t <me@my.email.com> -sf %temp%\subject.txt -server ServerName -f "SVN Admin <svn@my.email.com>" -noh2
The biggest gotcha in writing SVN hooks is that you might have basically NO environment set-up - no exe path, no temp path, etc. Though maybe that's improved in more recent SVN builds.
I use a post-commit script similar to this one.
It's sends a nice HTML email. I updated it some where it highlights code that was removed in red and highlights code that was added in blue.
You could use buildbot. It's a tool that can take arbitrary action whenever a check-in occurs. It's a full featured continuous integration system but if you just want emails it can certainly handle that. It has plug-ins for a variety of SCMs including SVN.
There is a (large) example written in Perl included in the Subversion source (it can be viewed here).