Dutch Sticks (6d4)

This method is based on a pretty simple device: a four faces long die. As shown in the picture, each side is marked with one of the possible lines (the red dot is just to help visualizing the die rotation).
Despite its simplicity (and the fact that long dice were known since ancient times), in 1997 a patent was granted to two Dutch guys for a method of casting I Ching hexagrams using six of these dice.
In his really interesting article on I Ching related patents, Steve Marshall suggests that the sticks  on Francina Pijl's site (where I've originally found this method) and shown in the image below might be the product that originated from that patent. For some time they were also available in US from Amazon.

 
The method is pretty simple:

1. Roll the six dice;
2. Stack them in order so to form an hexagram.

Probabilities

This method assign equal probabilities to each possible line:

Prob(6) = Prob(8) = Prob(7) = Prob(9) = ¹/₄ = 25%
Prob(yin) = Prob(yang) = ¹/₂

Variations

An alternative use of long dice marked with I Ching lines was devised independently by Lawrence P Kaster who advices not to use them for divination but for keeping track of the lines while casting a hexagram with other methods. The idea is that it would be easier to use them rather than having to stop and draw each line using pen and paper. And I do agree with him.
Lawrence has a shop on Etsy where he sells his I Ching related creations (and some more).

Hanna Moog posted a video on YouTube demonstrating how to use the sticks patented by Dominik Rollè in 2001 that use the same principle of the dutch sticks.
These sticks show, when stacked together, both the primary and the secondary hexagram which makes them very useful as a way to track the lines during the casting process.