Thank you letter??

Hey all! I just had an interview today and I am wondering now whether I should send a quick thank you letter to my interviewer. It is only for a clinical aide position but one that I really want in the NICU. If so, should I send it via email? Or snail mail? And what should it include?
Typically the rule is to send the thank you letter/email within 24 hrs after your interview. In this job market, do everything to secure the position.... which includes sending a thank you letter with the emphasis on your skills/qualification. Basically remind them why you are the right candidate.