Just wrote a little Safari extension that has two features:
1) Open new vBulletin posts in new tabs
2) Disable "onclick"-based navigation
After downloading and testing, I discovered it didn't actually fix the autotrader.com site, because they were using a global onclick handler. After some revisions (including splitting the two functions into separate extensions), though, the extension now works on ESPN, autotrader.com, and many other similar sites. It may not work for 100% of the sites out there, but it's been pretty robust in our testing.