I\'ve been dying for about 6 hours trying to figure out how to make a regular POST request in WP7 , I tried the answers of similar questions posted here and on many other places
For easier access to advanced http features check out these http classes:
http://mytoolkit.codeplex.com/wikipage?title=Http
It encapsulates GET, POST, FILES (using path or Stream objects) and GZIP (not directly supported by WP7) requests.
Stream