Allaire HomeSite used to be really good, until it got bought by Macromedia, which then got bought by Adobe. The code editing features got somewhat merged into Dreamweaver which is 10x slower, and although Adobe still sells HomeSite, it doesn't appear to be an actively developed product anymore. There haven't been any updates in a very long time. It's also a little buggy and crashes quite often (probably due to the fact that it hasn't been updated in ages).
Also tried WeBuilder 2008 briefly, but also found it to be quite buggy and crashed frequently, though it's got a good set of features and feels like a newer and better version of Homesite.
I've used Ultra-Edit in the past, which has lots of useful features and worked fairly well, and Notepad2 is also a good free application, though it seems better suited to quick changes rather than a full-blown IDE for Classic ASP development.