Readerware is sophisticated and provides server functionality, but it's painfully ugly and doesn't integrate book and media catalogs. On the upside, it syncs with Palm and Windows Mobile.
Delicious Library is very pretty and integrates book and media catalogs, but it doesn't provided any sort of server functionality, and it only runs on a Mac. It outputs to note files for an iPod for mobile browsing.
There's a solution, though, for the lack of server support. LibraryThing is a new web-based library catalog tool. It can export to delimited text files, and can import from Delicious Library's XML data files. Pretty schweet, and a permanent account costs only $10 right now. Very cool.
Now I've just got to get a Mac Mini. Too bad I didn't know that Frys was selling them dirt cheap this weekend.