I've created JAVA code for handling most of the routine things with common distributions, such as computing probabilities, quantiles, and generating random variates. I have written most of these things as Literate Programs in Noweb and I will make them available to the public very soon.
Although, the same thing is easily done for all the implemented distributions, only two applets that can be used to calculate probabilities under the normal curve and quantiles of normal distribution are presented.
The first applet below calculates areas under the standard normal density curves. You are presented with two fields and three buttons on top of a normal density curve. The buttons allow you to calculate areas to the left or to the right or between.
The second applet calculates quantiles of the normal distribution. You can choose any mean and any standard deviation. The applet will return the requested quantile.
Invalid input is ignored. You are just taken back to the offending field to try again.