Free VST host
Although obviously Sonar IS a VST host, it's handy to have alternatives, especially if you are having stability problems and would like to confirm whether or not a particular plugin might be the culprit.
I've just been playing with Psycle, which is a free open source project. To be honest, I'm very impressed, at least initially. It's slightly weird at first startup, because the first thing you see is a truly ugly configuration screen. Once past that, though, and once you figure out that you need to click on the gear rack, then add a 'generator' from your VST plugin list, then right click and drag a link to the master output, it seemed to manage hosting a copy of Mr. Ray, Organised Trio and a copy of Garritan simultaneously (as a more serious test) and play them back glitch-free.
Haven't looked at it in much detail yet but could be a useful host for live use, if it really is solid. Just thought I'd mention it, anyway... can't beat the price!