How does membrane potential vary between intraceullar membranes and the cellular membrane?
Yes, various intracellular membranes do have potential differences, but as you can imagine they are more difficult to measure experimentally, so in general data on this is scarce.

Summary


Mitochondrial membrane: 150mV-180mV with negativity on the matrix side. Seth et al 2011
Endoplasmic reticulum membrane: 75-95mV with negativity in the ER. Qin et al 2011, Worley et al 1994
Golgi: No notable membrane potential. Schapiro &amp; Grinstein 2000
Lysosomal: 20mV with more negativity on the cytosolic side. Koivusalo et al 2011


Discussion

The mitochondrial membrane potential is probably the best studied case. This is the potential difference over the inner mitochondrial membrane, between the mitochondrial matrix and the intermembrane space; it is about 150mV (more negative on the matrix side). There is also a potential difference between the mitochondrial cristae (folds of the inner membrane) and the matrix which is used to drive ATP synthesis; it is probably larger than 150mV, but this is still poorly understood I think. The outer membrane is permeable (has pores) so there should be no potential difference between the intermembrane space and the cytosol.

For the endoplasmic reticulum (ER), there is little data available I think, but there are some estimates based on measurements of ion transport, which gives a value of about 75 to 95 mV (more negative inside the ER). Probably this depends a lot on the situation, as the ER is involved in regulating ion homeostasis (notably Ca2+).

For the Golgi apparatus, this study found that no potential difference vs. the cytosol, based on the movements on H+ and counterions.

Lysosomal membrane potential has been measured directly, giving values of about 20mV (more positive inside).

For the nucleus I don't know of any data, but I would assume there is no potential difference here, given that the nuclear membrane has large pores.