Dean Baker, professional economist and co-director of the Center for Economic and Policy Research, has laid out here his ideas for financial system regulations in the future. As I find the contributions of others, I intend to add links to this post.
Brad DeLong, professor of economics at UC Berkeley, has a good post here. I strongly suggest skipping all the "economic science" stuff with crossing lines and reverse S curves and just read the "political economy" arguments that constitute the latter part of the post (starting just after the last graph). Of course, if you think it would make sense for your doctor to draw crossing lines on a piece of paper and say, "This is how your body works," dig into the wonkish stuff too.
Prof. Mark Thoma, University of Oregon, focuses attention here on the need to regulate the "shadow banking system." His post is followed by some good comments.
Bob Kuttner, co-founder and co-editor of The American Prospect and former columnist for Business Week, weighs in here.
Of course, I summarized Stiglitz's views in this earlier post.