This post, like all posts but more so, is my opinion, totally disclaimered, and likely out of date if you are reading this after TFS has shipped.
The issue that every newbie hits is that giving a user TFS permissions by right clicking on the TFS server node in Team Explorer and adding them to the Team Foundation Administrators group will in Beta builds at least not give you sufficient permissions automatically to create a new team project like you might expect. This is because creating a team project touches Windows Sharepoint and the SQL Reporting pieces, which have their own security subsystems that must be configured independently.
So, outside of the the IDE open a browser and navigate using an administrative account to the main Windows Sharepoint Site, click site settings, and then add administrative permissions for the user account creating team projects. Do the same on the reporting site, drilling down to the following page where you can add a new role assignment and add that user as a content manager.
Once the user account you are adding has sufficient privileges in (1) TFS, (2) SharePoint, and (3) SQL Reporting – team project creation should work like a charm.