I've shipped shrooms, cheato, and other softy stuff in a small thermos. Bag it up in the afternoon, take it to the post office, mail it priority mail. Cheap and easy.
I have used Fed ex, UPS and USPS. USPS is the cheapest for next day but will arrive late depending where u shipping it to. FED EX and UPS have a 10am next day arrival guarantee but they do charge twice as much.
I generally ship UPS ground if the destination is in the tri state area, UPS ground will get there next day for most areas in the tri state, I also ship ups 2nd day if its going across the country. If you pack it well they do fine.