Xmarks should work with a private server over WebDAV. You can register for a box.net account and get WebDAV access at box.net/dav. Of course, it is a short term

Xmarks should work with a private server over WebDAV. You can register for a box.net account and get WebDAV access at box.net/dav. Of course, it is a short term solution. If nice folks at Xmarks decide to open source the code, this could work out be a long term solution.