For later versions of Classic Mac OS, there was A-Dock[0] which I used quite a lot on my CRT iMac when running OS 9. It was pretty capable, with some features that the OS X dock never had. It supported custom themes[1] and played nice with Kaleidoscope schemes and Appearance Manager themes too, which made it awesome for desktop customization aficionados.

[0]: http://macintoshgarden.org/apps/a-dock-301 [1]: https://web.archive.org/web/20060103080636/http://jerome.fou...