I had problems with KiTTY: the session management doesn’t seem to work with multiple sessions. I looked for an alternative and found this one: http://jakub.kotrla.net/putty/. It’s basically a normal PuTTY with a patch to store Sessions on disk. It lacks the URL click-to-open feature, but I think I can live without it. I’ve been using it for 2 weeks now, and I’m happy with it.