Re: Attachments / File Uploads Plugin
I sure don’t, but Louisedade always said his Upload Avatar plugin was originally a file upload script he hacked to use avatars. It might be a good place to start.
Biggest problem you’ll have IMO is where to store post metadata. Usually I hate a plugin to add a table, but in this case it’s probably totally appropriate (and hey, if it works well maybe more plugins’ll use it and/or it’ll be taken into the core?).