Along with 3.5" disk releases of 8-bit software for education and games, the format became more popular with the introduction of the IIGS and the IIc+, and applications followed suit in this format as well.
The Apple IIc+ Software Directory is a collated list put together by Apple around the same time as the release of the last 8-bit Apple II model. It includes a comprehensive listing of software titles, although I'm sure errors crept in (Police Quest II for the Apple II? Can anyone confirm Sierra released their 8-bit adventure games on 3.5" disk?) and the list of course doesn't include titles released after the directory was put together. It's an interesting guide, however. If you have any of the titles listed that aren't included in this archive, please make disk images and scans of all available material, and submit them to the site so these rare titles aren't lost forever.