I’ve just discovered a nice little project, Grackle68k, which is a very basic Twitter client that works under System 6 to Mac OS 9. ‘Very basic’ means you can send tweets in a text field after authenticating and that’s it. On powerful vintage Macs — those who can handle Web browsing in a decent way, I mean — the best experience is probably using the Twitter Web interface. But for those who managed to connect their Mac Plus, SE, SE/30 etc. to the Internet, Grackle68k should do the job.
For the record, I attempted to use it in an emulated Mac OS 9.0.4 session under SheepShaver, but when sending the test tweets I got a “400 Bad Request” error. I guess it’s better to try it on a real vintage Mac. Too bad none of my compact Macs has a network card. I’ll try it on my PowerBook 5300 with Mac OS 8.1.
System Folder 
This app sorta works on my iBook Clamshell. But then again, it’s supposed to run on a 68K mac, is it not?