Microsoft have recently released a beta of a web developer toolbar, now there's nowhere near as many functions as the brilliant Firefox extension, but still pretty darn useful if you're trying to work out why your standards compliant website doesn't work properly in IE. Get It Here!
Thanks so much for that link. I've got a big list of CSS problems to solve this afternoon for a site which is IE-only (don't ask, seriously) and this has made my life a whole lot easier Sam