Simple file upload

I can't believe it's so hard to find a simple file upload script example for WordPress. Everything out there is so involved that it's hard to follow just to remove the parts I need.

I'm looking for a php script that will allow the user to upload a file, just like the attachment options at the bottom when creating a post to this forum. Just a simple "Choose File" button and an "Upload" button (just 1 file at a time is fine).

Could someone please point me in the right direction?

Thanks.

(sorry about the attachment - I was testing the upload portion, which worked without me pushing the Upload button)