I've seen a few that start from Catania...but i prefer to do one from Taormina. All the links in the search are years old. Help anyone?
Google is your friend...(this is only source - there are doubtless many others, and I'm sure you'll have choices even when you're on the ground)
http://www.viator.com/tours/Taormina/Mount-Etna-Day-Trip-from-Taormina/d4237-6099ETNA
Our hotel in Taormina sold us tour tickets for Mt Etna and we just walked a short way to the tour bus pick-up location.
We booked a driver for our trip to Mt. Etna and made some other stops as well, including a winery for lunch and an orchard. It was a fun day. A little pricey, but well worth it in our opinion. We booked it through legendofsicily.com.
Thanks, i ended up doing the same thing via viator.com