I need to instance object along spline. I'm already aware of Space Tool, but this is very basic.

Let's say I need to crate Palm Frond, I'd like to instance along both "sides" of spline as well as, to get leaves smaller as they progress to end of spline.

Is there any scripts of plugins out there, that will allow me to that without manually adjusting every object ?

Animation- path constraint.
Do this with keyframes to get the desired scale : )

Also check out the Spacing Tool.
http://download.autodesk.com/us/3dsm...mber=d28e60752

Maybe check this out, too:

http://www.scriptspot.com/3ds-max/sc...j2spline-align