SimpleDice is a lightweight, straightforward die roller program. Here I will mention its basic features.
The basic interface can perform simple die rolls as well as custom rolls of the format XdY+Z, where X is the number of Y-sided dice, and Z is a constant integer.
If you need additional functionality, the ">" button at the top-right will expand the window to include advanced features.
Roll history: this box records the results of all of your rolls since you opened SimpleDice.
Save button: this allows you to save your roll history as plain text for future reference, if needed.
Custom roll formula box: this neat little box allows for more complicated formulas that include multiple terms with addition, subtraction, and "drop the lowest" functionality, as in 4d6 drop 1. Just type your formula and hit enter.
Percent button: this displays a bar along the bottom of the window that keeps track of how many rolls have been above, equal to, or below average, so you can prove to your GM how unlucky you've been in that troll fight. It unfortunately won't work for formulae typed into the custom box. This is because it is actually kind of difficult to calculate average values for the "drop" operation.
Mute button: this mutes the dice rolling sound.
Currently, the custom roll formula box gives an error when mixing + and - operators. I haven't had a chance to look into this yet, but it's on my list. It only minimally affects the program's usefulness.
Also, the window resizes oddly the first time a die is rolled. I know how to fix this, but haven't gotten around to it. It's just cosmetic.