Imagine if there was a tool that could perform any salary cap operation you can think of - from declining options to waiving a player to buying a player out to renouncing a cap hold to changing where you pick in the draft, to making a trade to signing new players via space, or re-signing your own players, that automatically calculates everything for you, so that you can see the total payroll, cap room, room under tax, tax payment (if any), & room under the apron, for the current season and three following, instantly after performing an operation.
...well, there is now.
New @ ShamSports of all places (yes it still exists): INTRODUCING, The Capulator.

The Capulator is exactly what the portmanteau in the title suggests. It is an NBA salary cap calculator. Rather than writing out cap scenarios, users can essentially draw them, save them, and share them.
Ever written an offseason planning piece in which you devise various moves for your team, and create all kinds of charts and descriptions and whatever else to show your working to people? You needn’t now bother. Come here and draw it.
Open The Capulator. Do whatever you want in it. Hit the save button. Save the unique ID. And that's it. Congratulations! You just created a hypothetical, and a shareable one at that.
Be as fantastical or as realistic as you choose. The Capulator is not deterministic, and need not be realistic if you don’t want it to be. What it will be, it is hoped, is militarily precise about what is legal and possible. It does not tell you what to do. But we are hoping it does tell you what you can do.
We have beta tested it, and gamma tested it. And yet, through the sheer complexities of size and scale, there will no doubt be things we have not thought of. We therefore kindly ask you to let us know at the usual address. Specifically, advise us of any of the following:
a) whether the thing works properly in accordance with the rules of the cap (the key one - there's so many rules and intricacies, and we try to honour them all; the only deliberate omission is the Over-38 Rule, which was not realistically programmable),
b) whether it functions properly as a tool, and
c) whether there's anything we've missed.
Note also a couple of things that the Capulator isn’t. It is not a trade checker – while the ability to add and remove contracts via (imaginary) trades is key to forecasting cap situations, you must verify the accuracy of such hypothetical deals for yourself. (Use RealGM’s Trade Checker for such.) It is also not especially smartphone friendly. Maybe soon, but not yet.
What it is designed to be, however, is extremely user-friendly.
Please explore it (guide attached, but the basic gist is - salaries at the top, cap holds at the bottom, roll over them to explore the options for them, use various exceptions by hovering over them at the very bottom, and do trades and minimums using the "transactions" bit at the top). Let us know what you think. And happy, err, transactionising!
http://www.shamsports.com/capulator