Video games...

There are two modern adventure games for the PC, which are based on the novel.

The first game is simply called Treasure Island. It was developed by Radon Labs GmbH and published by DreamCatcher Interactive Inc. in December of 2009.
It's not a great adaptation but it is often fun and it does keep some of the atmosphere of the story. It changes the ending slightly and that might be its biggest sin, since it's kind of a downer if you care for the side characters. It also adds a love interest for Jim, but that turned out not to be as annoying as it sounded.

Review:
http://www.gameboomers.com/reviews/Tt/TreasureIsland/TreasureIslandbyBecky.htm

It gives you several hours of gameplay and it might be worth 5 bucks if you're a big fan and want to see every iteration of the book.

Short gameplay video:
http://www.youtube.com/watch?v=JHNwKksVHYg



The second game is called Destination: Treasure Island. It was developed by Kheops Studio and published by Nobilis/Dreamcatcher in 2006.

This on occasion hard puzzler is an entertaining continuation of the book. If you don't mind having some fun with the storyline (and don't expect a new novel worth of story) this is a very nice short epilogue to Jim's adventures. The game looks great, the acting and writing is just fine and you get to tie up all the loose ends from the book.

Review:
http://www.gamespot.com/destination-treasure-island/reviews/destination-treasure-island-review-6177533/

The game can be beaten in a couple of hours if you don't get stuck somewhere (and you will), but it's still worth 10 bucks if you crave for more adventures with Jim (this time there's more brainteasers than swashbuckling though), and get that "good" (instead of ambiguous) ending you always wanted for the heroes of the book.

Playthrough (worth seeing just for the weird puzzles, beautiful looks and fun storyline)
http://www.youtube.com/watch?v=nhwgBouFKKo



And if you're a fan of the Muppets, there's always the Muppet Treasure Island, released by Activision in 1996. It's partially an FMV adventure game based on the movie Muppet Treasure Island from 1996 http://www.imdb.com/title/tt0117110/ .

Review of the game:
http://www.pibweb.com/review/muppet.html

This is a fun game for Muppet fans (not sure about the book fans though) and it's definitely worth up to 5 bucks even if it can be beaten in a couple of hours.

Playthrough (again, watch it just for fun if you don't want to buy a short game)
http://www.youtube.com/watch?v=n_VYMcZUzr8