Main calibre site -
http://calibre-ebook.com/ - does not have any recipe collection, only help files on how to create new one.
However, it's quite technical and very few people will finish that for their favorite sites.
Built-in list of recipes is very small and definitely not enough for many calibre users.
This question is mostly to Kovid, but if someone else can do it, it will be great.
Two important features are user flags (working\not working - because sites can stop working after redesign) and download counts.
Anyone?