A major focus of the PHENIX experiment at the Relativistic Heavy Ion Collider is the study of proton spin structure using polarized proton beams. In longitudinally polarized proton collisions, PHENIX is able to study the gluon spin contribution to the proton spin. π⁰ A_LL results from 2005 and 2006 have been shown to constrain Δ_g. With an increased figure of merit, due to higher luminosity and polarization, new probes have become available, such as π^± and η. Earlier results for single spin asymmetries using transverse polarization have been shown. A significant transverse data set in 2006 will soon yield results.