For random templates, I have a folder called (wait for it...) Random Templates, hahaha! No, really - I do! I throw all kinds of free templates in there. I just rename the template with where I got it & what month... for example "GirlTalk-July09" (I then know I got it on Dani's blog (Girl Talk blog) and it was the July challenge template.
Odds and ends get put in a Miscellaneous folder with the product name on the folder. I just be sure to keep the credit info in the folder so I remember who created it.
PS - it sounds like you'd benefit from having an organizing system like ACDSee, where you can tag all your items without having to move peices all over the place
