Google Webmaters Tools does let the webmaster set the Preferred Domain
Preferred domain [?]
If xwww.slottipsguide.com and slottipsguide.com point to the same site, you can tell us here how you want URLs to display in our index.
Display URLs as xwww.slottipsguide.com (for both xwww.slottipsguide.com and slottipsguide.com)
Display URLs as slottipsguide.com (for both xwww.slottipsguide.com and slottipsguide.com)
Don’t set an association