Can anybody tell me if there is a way for me to get the domain name of my site in the Application_Start event in the global.asax?
Normally I'd just get it from Context.Request.ServerVariables["SERVER_NAME"], but this is not available. I'd ideally also like to get the URL from the request that kicked off the application.
Hmm - from answers below, it would seem that being on IIS7 makes a difference here. This is new and there are now design guidelines to try and stop you from doing it:
You can access the Context through the static HttpContext.Current member.
HttpContext.Current.Request.ServerVariables["SERVER_NAME"];
HttpContext.Current.Request.Url;
Edit, Based on some of your comments I did some additional research
This error is due to a design change in the IIS7 Integrated pipeline that makes the request context unavailable in Application_Start event. When using the Classic mode (the only mode when running on previous versions of IIS), the request context used to be available, even though the Application_Start event has always been intended as a global and request-agnostic event in the application lifetime. Despite this, because ASP.NET applications were always started by the first request to the app, it used to be possible to get to the request context through the static HttpContext.Current field.
So you have two options