Debian 3.0r2 Released
I like debfoster over deborphan, depending on what I'm up to.
The upside to debfoster is that I have the option of walking through all of what I'm going to call the "top-level" packages on my system - those that are not installed as dependencies, but something that I installed for my own evil purposes. Then, for each such package, it tells me which packages are installed because of it, and gives me the option to review its package information, and keep it or give the package its walking papers.
This way, I'm not limited to libraries without dependent applications. Any package is subject to scrutiny, depending on the configuration.
I still use deborphan on occasion for quickly getting rid of a library or two, but I use debfoster followed by cruft for "spring cleaning".