I present the rheological properties of graphite oxide sheets (GOS) and functionalized graphene sheets (FGS) in various solvents. Exfoliation of GOS and FGS are obtained via sonication of strongly oxidized graphite and rapid thermal heating of graphite oxide, respectively. AFM experiments reveal that the majority of the exfoliated particles are single sheets with a high surface area (~1500 m2/g) and aspect ration (100-10000). The effects of commercially available fuel detergents and surfactants on the dispersion and resultant rheological properties of GOS and FGS suspensions are studied in oil and water. The intrinsic viscosity measurements of the suspensions are related to the aspect ratio of the sheets using theories available for obliate spheriods and these results are compared to AFM data. The orientation of the seets with shear is studied by dichroism measurements. The effects of sonication time on suspension rehology and particle dimensions will be discussed.