Hey runequester; Well, I've been using 3.9 for a while, I'm pretty sure most of these are cool under 3.1.
-Magic Menu V. 2.30 (improves look and operation of menus)
-PowerSnap V2.22a (allows cut-and-paste text between almost any amiga programs)
-MCP (Grrr, it does pretty much
EVERYthing, not gonna list it all...) Note: some ppl think MCP is a buggy bit of *^&^, but I've used it for years, no problem
-ReqAttack 1.1 (Improves requesters, mostly cosmetic)
-ToolsDaemon (allows you to add menus, sub-menus, hotkeys, etc.)
-some virus checker (there might be virii around on old disks..)
-FBlit (helps to conserve Chip RAM usage)
I'm sure others can add to the list...
