Subversion repositories served with Apache have the nice built-in feature: the repositories can be browsed with any webbrowser at no additional cost.

For Subversion repositories served via svnserve, this is not possible because browsers don't understand that protocol.

Until now:
The SVNProtocolHandler for Internet Explorer allows browsing svn:// urls from within the Internet Explorer. No need to install a Subversion client, just use Internet Explorer. This also adds the benefit that you can click on svn:// links and quickly the URL you received from a colleague via email.

Note: the protocol handler only works in Internet Explorer. Chrome, Firefox etc. users either have to switch back to Internet Explorer for SVN browsing or hope someone will create an svn:// handler for them.

The installer for the SVNProtocolHandler can be found on the download page.
Note: even though the SVNProtocolHandler is developed by Stefan Küng, it is not part of TortoiseSVN and won't be included in TortoiseSVN either. It will remain a separate download, and it has its own project page.