While there are a lot of places you can find Flash files, I haven't seen very many good ones. I do know that in MX 2004 & Flash 8, there are Macromedia-made templates you can choose from when creating a new document.
What kind of template in particular are you looking for?
flashkit.com has lots of .fla files you can download and many of them are templates - they also have lots and lots of tutorials and a large forum. I think a lot of the stuff is pretty old, but most of it still relevant.