What the heck is WISP? If you haven’t heard of it, it stands for Web Interface for SharePoint. Basically it’s a set of web parts for SharePoint that let people use their SharePoint portal as their Web Interface instead of building a Citrix Web Interface server.
The new 2007 version of WISP can fully integrate with SharePoint, including content redirection and (if you're using SharePoint Portal Server), single sign-on.
Citrix has a fantastic 18-page “Getting Started” guide. Rather then paraphrase what that guide says here, just go to the source and read it. They’ve also set up a WISP 2007 forum on their support site.