Computer casting

There are currently many sites and applications that will generate a hexagram for you. Most of them offer links to commentaries to directly get an interpretation of the hexagram and some also have the possibility to switch between the yarrow stalks and the three coins method probabilites.

While, conceptually, casting hexagrams is an extremely simple task for a computer, there are drawbacks that you should be aware of.

First of all, generating true random number on a computer is extremely difficult. In most cases the program will use the default pseudo-random number generator (PRNG) which, usually, will trade speed for accuracy and generate numbers that are not random at all.
A PRNG will generate a sequence of numbers that is completely fixed once an initial seed is given, however some of them are able to generate sequences that appear to be random to the most common statistical tests. If unbiased randomness is important to you, you should check whether the software you're using has a good PRNG or not.

Second, using a program to cast the hexagram may lack that feeling of a direct connnection between the user and the response: you click a buttom and you instantly get a line (or even an entire hexagram). The experience of counting, shuffling, throwing, etc., is completely taken away, just a click and you're done!
This may be a problem for some (me, for example) and may discourage them from using casting software; others, instead, like exactly the fact that the response is immediate and they see a profound connection of the response with the exact instant in which the question is formulated.
Being a matter of personal preference, it will be up to you to determine if using software is for you or not.

If you come across a softare hexagram generators, to decide if you are going to use it or not, you may want to investigate if it uses one (or more) of these strategies:

1. Use the random number generator available to the language/operating system the software runs on.
2. Use a hardware true random numbers generator (e.g. using white noise radio signals, nuclear decay, ...).
3. Use the date and time to link the hexagram to the time it is cast.
4. Incorporate element from the user (e.g. mouse movement, keyboard tapping).

I wrote a small line hexagrams caster, which uses the two last strategies mentioned above to increase the participation of the user to the casting process. The applet collects random bits from the users mouse movents and clicks and use them to generate the lines (with yarrow stalks probabilites). You can see it in the right bar of this site.
Clicking on the numbers below the response will get you to one of the many sites that offer I Ching commentary text.

Please note that it is not very mobile-friendly (it's somhow bothersome to have to tap many times on the image), I hope I'll have the time to improve it some day.