Oral B does. If you are a Dental student, contact your school's ASDA leader and ask for the website/P&G representative. They will set you up with what you need.
Dental-Professional.com is the only site still offering free samples. Colgate and Crest stopped last yr. They only give away a specific # of samples each month so its best to put in your order on the 1st of each month. Just did mine today and still some samples left for Sensodyne and Pronamel toothpaste.