I'd like to recommend this damage calculator that I've been using for about a year now.
luungoc2005's Generation 5 Damage Calculator
It hasn't been updated in a while, but most of the necessary sets are in it. Also, it has a really nice interface. I know it isn't "a C&C project", but it should definitely be on the list. Also, if you right click on the "Defender" or "Attacker" labels on top of each Pokemon box, you can import PO sets and export sets to PO format. Implementing stat boosts is also a breeze, as is anything not legal. Wonder Room, Critical Hit, Multiple Targets, and No Immunity can also be accounted for. Gender, Level, Status, Weight, Happiness, and HP Percent can all be changed. Flash Fire, Me First, Helping Hand, and Metronome counter may be accounted on the offensive side. As far as defensive options, hazards, screens, Mud Sport, and Water Sport can be accounted for.
252 +2 SpAtk Life Orb Thundurus Thunderbolt vs 4 HP/0 SpDef Chandelure: 81.68% - 96.56%
2 hits to KO
Possible HP Damage: 214, 217, 220, 222, 225, 228, 229, 232, 235, 237, 240, 243, 244, 247, 250, 253
You will also get a neat little description that says the possible HP damage and relevant investment and stat boosts of each Pokemon. Weather is also an option to set.
Reverse calculations are also easy to make. Moves and abilities may be filtered out. You can even change the base stats of each Pokemon to screw around. This is much easier than implementing types into the old calculator. Many targets for one attack may be chosen, and multiple specific defensive and offensive calculations can be made. Also, calculating stats of Pokemon quickly is very easy. You can also make up moves if you want to, even though other calculators can do it, it is easier to do. Also, you can right-click and install the calculator straight to your computer. The last neat little quirk is that you have a coverage calculator where you can pair the types of four moves together and see what coverage they get together.
Sorry for the kind of long post, and I know this isn't C&C work, but this calculator should have a link. Cheers!