This question has been answered by BobRay. See the first response.
[[*title]]
[[*longtitle]]
A MODX resource (e.g., the current page) has no title field unless you've created a Template Variable called 'title' (without the quotes). In that case it would be:
[[*title]]
You might mean the longtitle field, which would be:
[[*longtitle]]
The available fields for a resource are listed here: http://bobsguides.com/modx-object-quick-reference.html#modResource
<title>[[*pagetitle]]</title> <title>[[*longtitle]]</title> <title>[[*menutitle]]</title> <title>[[*introtext]]</title>
<title>[[*mytemplatevariable]]</title>
<!DOCTYPE HTML> <html> <head> <meta charset="[[++modx_charset]]"> <title>[[*mytemplatevariable]]</title> </head> <body> [[*content]] </body> </html>