You can also use svnsync to create a copy of your repository.
This requires adding a pre-revprop-change hook on the destination repository (and requires a Subversion 1.4 or newer repository at your hosting provider).
After you svnsync'ed your repository to a system you manage, you can use svnadmin to dump the local copy if you need a dumpfile (or just use the synced to repository).
[Update in 2011:]
Since Subversion 1.7 there is a tool called svnrdump
which you can use to create a dump file from a remote repository in a single step.
svnrdump
. It appeared in svn 1.7. – bobbogo