Most of the crap I buy from Craigslist can be paid for with $20's, so I actually do just show up with a second person and cash a lot.
Now on the more serious transactions, I will come with a blank bank check and meet them at their house. If I like the car I can hand over the check or we can go to their or my bank (credit union) for verification/release of funds/cashing and title signage.
