We present a numerical method for computing the Stokeslet and stresslet integrals in Stokes flow, motivated by applications such as swimming of microorganisms, particle and drop motion, or biomembrane and red blood cell mechanics. Evaluating the integrals accurately for points near the boundary, e.g., when two interfaces are close together, is the most difficult case. The accurate solution is obtained by regularizing the kernels and adding analytically derived correction terms to eliminate the largest error. On the surface, high order regularizations are designed so that corrections are not required. To evaluate the resulting sums efficiently, we developed a kernel-independent treecode based on barycentric Lagrange interpolation.