I think
most ISPs have dropped NebuAd, at least until all the congressional questioning is finalized and a number of privacy concerns are addressed.
As for software to stop the actual tracking itself, I run Adblock Plus with the ABP Tracking Filter, but I'm not so sure that it will stop NebuAd tracking.
Check the broadbandreports.com website for frequent news updates regarding the NebuAd fiasco.
Edit: Here's a listing of at least some of the ISPs that partnered with NebuAd:
NebuAd - Wikipedia, the free encyclopedia
I'm not sure how many (if any) are still involved with NebuAd, but I suppose if there's enough money in it for the ISPs, some or all of them could still be involved, but just keeping it quieter since there was such a big uproar from consumers and a potential problem with it as indicated by some congressional members.