I have to use CVS quite often and from time to time I'd like to use it directly from Nautilus. There was a project 'nautilus-cvs-scripts' that could be found at http://jodrell.net/projects/nautilus-cvs-scripts. Unfortunately it was dropped, but the SVN version is quite similar and based on the CVS version. So I took this one and re-worked it. It's still far from completeness, but works at least for me now. If you like it feel free to download and use it and to send in patches ;)
It uses zenity to display the GUI elements which makes it very easy to change things.