Are addresses and dates of formal letters punctuated or not?
It depends; in BrE they use different formatting than AmE.
In AmE, the only punctuation in the date is a comma separating the day from the year:
October 14, 2007
In the address, you'd use period after any abbreviaion, such as "Mr." or "Ave." (avenue), and a comma between the city and state (if you're mailing to a US address):
Mr. Martin Crane
123 Heugenot Ave.
Seattle, WA 90420
Ms. Bernadette Yao
P.O. Box 359
Boston, MA 02134