Live Search Web Part
I have pre-configured a Web Part for MOSS that you can just drop on to a Search Center results page. It will run the current query on Live Search and display the results. It is built using SharePoint Designer, the Data Form Web Part, and the Live Search SOAP API. It automatically retrieves the current search keywords from the Query String, and you can also edit a couple of static parameters in the .webpart file.
Nota bene: the Web Part is contained in the MSN_Search_Service.webpart file attached to this post: 8 KB only, and no code required!