[wp-hackers] best method for figuring out where a plugin is.

[dubayou]

im working on a plugin, and when im building links i dont know to call

?page=widget-profiles/widgetprofiles.php
or
?page=widgetprofiles.php

in the code if i use just __FILE__ it fails if its installed in a folder?
know i have a little monkey hack to fix it for now, but whats the best
way to get the installed path of your plugin.

ps. check out http://wordpress.org/extend/plugins/widget-profiles/