When a colleague first introduced me to ASP I was totally underwhelmed and didn't understand why you'd use it when you could write your own ISAPI extensions (silly me). Some time later I finally saw the light and thought it was great. In fact it became my primary coding tool for the following 3 years.
Well a lot happens in 3 years, and now I think ASP is of very limited value. I won't say ASP itself sucks, but I will say that most deployments of ASP suck.
Essentially, ASP is bloody fantastic on a perfectly set up web server, OK on a normal web server and bloody awful on a machine where the system administrators always install the latest and greatest of everything. (see more below)
Unfortunately, whether your particular server is great or bloody awful is normally out of your control, and as such I've completely gone off ASP and am going back down the ISAPI path with a leaning towards XML/XSL. However, I've collected several good ASP related links which are probably a little out of date by now, but here they are anyway.
ASP is nothing more than scripting for any COM component that implements the IDispatch interface. Period. By itself, ASP can't do a single thing, but the power of ASP is that you use COM components to do anything that is possible on a computer and really great when it works.
Unfortunately, the power of ASP is also its downfall. The COM components that provide heaps of functionality for ASP also dictate the stability of your web server. Your site is at the mercy of any COM component installed on the machine, and its interaction with every other DLL and COM compoent, and that includes the ones from Microsoft which like software from every other company is not always perfect.
Hence, installing an update for almost any COM component, DLL or application can totally change the stability of your web site, for better or worse, and as such, ASP is a nightmare to maintain unless your machine works perfectly and you never upgrade anything at all, which is a great plan but in practice never works.
Q.E.D. - I prefer not to use ASP any more.