Pale Moon. I know it's still technically under development, but it's gone to shit.
I think it'd be cool if some of the old software and operating systems like Windows 9x was made open-source for hobbyists, so we could get things like updated drivers and modern network compatibility making it easier to build a retro gaming PC, but I doubt Microsoft would ever do something like that.
I talked about MSN Messenger in another thread.
Usenet is still there and still works, but is largely abandoned outside of Filez. It's be cool if there was a revival and there were people to talk to on it again, because it's decentralized and censorship free.
This reminds me of RSSowl, and excellent feedreader thant's been abandoned since 2013. You used to be able to use it to scrape the entire text from the link in the RSS feed to avoid actually having to open the browser to read artilces.