For the bus connection, take look eurolines.ee or eurolinespolska.pl . You can buy tickets online and then just go to the bus station.
For the ferry (operate all year):
Then there are the companies operating the fast vessels, but these do not operate during the winter or bad weather (what is considered bad, is usually told on the company website).
Linda line (until 6.10.)
I was one flying with Blue One (cheap branch of SAS) but I don't know if this connection exists
Blue1 connection to Warsaw will not be operated during the winter, based on what I have hear from somewhere.