PiP for Mac - Always on top window preview similar to the popular windows only OnTopReplica
Hitomi Downloader - Desktop application to download images/videos/music/text from Hitomi.la and other sites, and more.
Pennywise - Cross-platform application to open any website or media in a floating window
HakuNeko - HakuNeko is an all-in-one cross-platform utility that supports you to download manga and anime with various website support.
Afloat - Create beautiful invoices in 3 clicks, without mistakes
HDoujin Downloader - A powerful doujin/manga downloader that supports hundreds of different websites.