I would start by calling people that sell firewood or a logging outfit. Iam sure they could get headed in the right direction.-- Just a thought-- Upnortdareh

In Watertown we have a wood, compost and mulch pick up site that is open 24x7. There are large wood pieces there frequently. Trunks 2-3' in diameter and tall.

Perhaps Madison has similar sites?

Otherwise definitely call tree trimming services, they will be able to get them although you may want to call a few to get prices, some folks might want to charge a lot and others might just want a few dollars for a truck load.

If you can haul your own that would (should) make it cheaper.

You might want to call Hamm's ArborCare, a professional tree service at (866) 596-5396. Their service area includes greater Columbia and Dane counties with shops located in Windsor and Pardeeville.
I get free mulch from them every summer. Talk to Kevin Hamm. They trim (& cut down, if necessary) some really BIG trees.

Hope this helps

Here is a link that might be useful: Hamm's website

If you are near Madison, they just finished thinning the thick growth of trees along Northport Drive/Hwy 113 near the dog park, by Cherokee marsh...tons of big old trunks and pieces just laying there, I wonder if people could just take them. I think they're just waiting for the chipper.