  Recent highlights from the spin program at the Relativistic Heavy Ion
Collider (RHIC), focusing on the gluon contribution to the proton spin and the
polarization of the light flavor sea, are presented. The impact of these data
on recent global fits by the DSSV and NNPDF groups is also discussed. Finally,
this note examines the constraints on the longitudinal spin structure of the
proton which would be possible with a proposed eRHIC facility.
