I think these days less is more.
Don't put site wide links to external websites, and only add something that will add value. Don't add clutter for clutters sake.
In reality, most people won't really see the footer of your website as a primary place for info, so keep it simple.
Look at the footer on any page of our business directory, lots going on, loads of information. But from heat maps we know very little is used.
The forum footer is much simpler, limiting to a disclaimer, biz info and social media links.
But my favourite is our Trusted Trader site which has a much simpler and clutter free footer. So it looks like we are evolving to a simpler approach.