ASP, or Active Server Pages, is not actually a language. It is a system that uses the Windows Scripting Host to execute code, and exposes a few objects (Session, Response, Request and Server) to allow code written for the Windows Scripting Host to talk http.
ASP is a Microsoft product, packaged with their IIS webserver.
Usually, ASP is just used with VBscript, a derivative of VisualBasicLanguage. However, any language that lives in the Windows Scripting Host can be used to write ASP pages; for instance, Microsoft's JavascriptLanguage implementation is built in the Windows Scripting Host, and so Javascript can be used to write ASP pages. Activestate's perl distribution integrates with the Windows Scripting Host, so you can use it to write ASP pages in perl.
There are several competing ASP tools; one was made by a group called chillisoft, but has now been bought by sun, see http://wwws.sun.com/software/chilisoft/index.html for details. There is also a project called Apache::ASP (http://www.apache-asp.org/) which produces the ASP programming model in the perl programming language, much like Activestate's integration with Microsoft's ASP, and runs in the Apache webserver.