Composites of aligned single wall carbon nanotubes (SWNTs) are among the most sought after materials in nanotube science. We have recently created nematic nanotube gels, aligned composites consisting of homogeneously dispersed surfactant coated SWNTs at low volume fraction in a cross-linked N-isopropyl acrylamide polymer matrix. An isotropic-nematic phase transition of the nanotube gel was induced via a volume-compression transition of the polymer matrix. These gels exhibit hallmark properties of a nematic liquid crystal: birefringence, absorption anisotropy, and disclination defects. The gels have also enabled us to probe absolute optical absorption cross-sections and anisotropy of the carbon nanotubes, as well as alignment mechanisms of SWNTs in an external magnetic field.