title: General sparse iterative solver libraries
body: <p>What are some of the better libraries for large sparse iterative (conjugate gradient, MINRES, GMRES, etc.) linear algebra system solving?  I've often coded my own routines, but I'm interested to know which "off-the-shelf" packages people prefer.  I've heard of PETSc, TAUCS, IML++, and a few others.  I'm wondering how these stack up, and what else is out there.  My preference is for ease of use, and freely available software.</p>