By saving a file sitepoint_forums_onebox.rb in the lib/onebox/engine folder
module Onebox
module Engine
class SitepointForumsOnebox
include Engine
matches_regexp /^http:\/\/www\.sitepoint\.com\/forums\/.*/
def to_html
"<iframe src='#{@url}' style='border-width:0' frameborder='0' scrolling='no' width='100%'></iframe>"
end
end
end
end
Needs some Design Love