I have uploaded my latest screencast, Episode 029, to screencasters.heathenx.org. This episode is pretty short. I demonstrate how to make a custom color palette in Inkscape. The palette file (.gpl) is basically just a text file with (r,g,b) colors and a name for the palette. Below is an example:

GIMP Palette
Name: My Palette Name
Columns: 3
#
0 0 0 Black
255 255 255 White

Since Inkscape uses the same color palette files as the GIMP then one can copy palettes between GIMP and Inkscape just by copying and pasting the .gpl files into the “palettes” directory. Simple stuff.