Weak gravitational lensing has emerged as an important cosmological probe for our understanding of dark matter and dark energy. Cross correlations between lensing and galaxy over-density map the stacked matter distribution around galaxies and provide important information about matter correlations and the growth of large scale structure. I will present our measurements of galaxy-galaxy lensing and galaxy-CMB lensing cross correlations using SDSS III-BOSS spectroscopic samples with SDSS galaxy lensing and Planck CMB lensing. I will also address some of the issues in covariance estimation for these measurements. When combined with galaxy clustering and RSD measurements, these measurements also provide strong constraints on the standard cosmological model. As applications of these measurements, I will discuss the recent measurements of the E_G parameter that quantifies deviations from general relativity, cosmological parameter constraints and the estimation of relative calibration uncertainties between galaxy shear and CMB lensing.