Sven,
Here are some useful links on Cosmology and expansion.
http://members.iinet.net.au/~sjastro...andingUniv.pdf
http://members.iinet.net.au/~sjastro...ance_scale.pdf
http://members.iinet.net.au/~sjastro...y/acc_univ.pdf
Then there is Ned Wrights tutorial, somewhat more technical but it goes some way to explain the diagrams in ariv.org link which is central to understanding the paper.
http://www.astro.ucla.edu/~wright/cosmo_01.htm etc.
This blog which Shiraz pointed out has some valuable information on cosmology.
http://www.preposterousuniverse.com/blog/
Our measuring sticks on a global (cosmological) scale do expand, but on a local scale the sticks are rigid for two reasons.
(1) The effects of expansion are minimal on a local scale.
(2) Local scales are generally associated with gravitationally bound systems, (Earth, Solar system, galaxy, local cluster) where gravity prevents expansion from occurring.
This can of course can change if dark energy increases with time in which case in the very distant future expansion might occur even at the smallest scales.
The Planck level is the quantum mechanical version for spacetime of the
Compton wavelength for an object.
If you shrink an object down to its Compton wavelength it no longer behaves as an object described by classical physics but is quantum mechanical in nature.
Similarly spacetime at very small scales is quantum mechanical in nature.
A "point" in spacetime is undefinable due to uncertainty in the "position" of the point.
It is one of the problems with General Relativity being a scale dependant theory.
Point sources such as Black Holes should in theory not exist as spacetime at such small scales should "smear out" the point source.
Similarly our knowledge of the Big Bang only goes back to 10^-43 second after the bang as before this the Universe was quantum mechanical.
Steven