I've got some functions coded that I want to add into my AS dictionary (the
same way the http://www.laco.wz.cz/tween/ integrate directly into the
API)...I've tried setting this up as an extension according to the sparse info
around the net but I havent had any luck (as most tutorials are for making
components).

Can anyone shed some light on the topic?

To package a extension you need two things, the macromedia extension manager
installed, and a .mxi file for your custom extension. The .mxi file contains
the information needed to tell the extension manager what type of tool it is,
how to make use of it, and info displayed during installation, files to use etc
etc...

Its much easier to get your head round a mxi file when you've got one infront
of you as a reference, theres just too many tags to fill out to go through
here, but once you've got one its easy and is just in a xml format. Just
searched my commands folder for a example you can download, if you go to the MM
exchange and download the "A3D_developersAssistant_1" then look in your
commands folder theres a pretty good one there.

Hope that helped, dr_ross