So we've made the switch to our site, running on Joomla - but most the major internet search engines still are directing people to information on the old site. And that site doesn't exist. So I've set up a meebo widget on our 404 page.
It's a test thing - and will only be staffed when I'm around my computer. And doesn't work for folks using our internet filter in the library - but for those using unfiltered internet and out in the big wide world - it should work.
I'll let you know how it goes. :-)