June through August, the commercial jet flies daily to Gustavus - a quick 15 minute "hop" from Juneau! Book your flight directly at Alaska Airlines.
The ferry services Gustavus year-round out of Juneau. The cruise length is approximately 4 to 4.5 hours each way, sometimes with a stop in Hoonah along the way. A great option if you're not in a rush!
More info at Alaska Marine Highway System.
For more flexibility in arrival and departure times, Alaska Seaplanes offers several flights to and from Gustavus every day of the year!