Ubuntu includes the free commercial URW++ postscript fonts in /usr/share/fonts/type1/gsfonts (from the gsfonts package).
I've seen that the full set are also available in TrueType format (including several not in gsfonts, such as Garamond). If you download the ghostscript source, they're all there.
Is there any benefit to using the TrueType versions instead? Will the display improve? Will it affect printing?