Does anyone know of any ways (as inexpensive as possible) to travel from Maui to the other islands other than flying? Thanks.

Swim or canoe

Fishing trawler.
Good chance to brush up on your Barnacle Bill the Sailor songs.

Anti-matter transport device.

Chinese immigration runners have to take empty ships back to China after dumping their stowaways in California.
I'm sure they'd offer you a nice deal.
Ask for a deluxe piece of cardboard to sleep on and a spot on the floor next to the bathroom (porthole).

kjp--

ferries run from maui to lanai and molokai. and for transport btwn maui and the other major islands, american hawaii cruises does (one-week?) cruises by ocean liner.

All kidding aside, the only way to travel to and from the majority of the HI islands is through interisland flights. They operate through Aloha and Hawaiian Airlines. Prices are less if you buy a booklet which contains air coupons that are greatly discounted from what you would pay on the open market. I don't know where they can be purchased but I'm certain someone on this site could provide that info for you.