The Aptana Studio IDE (my drug of choice) generates hidden .tmp files whenever you edit a PHP or HTML file. These are used generate the HTML preview within the editor. For those of us who don't use the preview feature, these files can be a nuisance.
Preventing Aptana from creating these files is simple. All you need to do is set the "HTML/PHP Editor Mode" to "Source only" in the Aptana -> Editors -> HTML and Aptana -> Editors -> PHP sections within the preferences.
Alternatively, you can create a handy little script to manually remove all .tmp* files.