Many times when you have a user filling out an InfoPath form, you would like to auto-populate some of the fields with the data from the current user's SharePoint profile. I found a nice reference here:

http://blogs.microsoft.co.il/blogs/itaysk/archive/2007/04/05/InfoPath-_2D00_-Get-the-current-user-without-writing-code.aspx

And I confirmed this technique still work in SPS 2010 and InfoPath 2010. When looking for property names, use the internal property name which can be found by editting the property in the user profile service application.