VRay Render Mask Maker
This script allows you to paint multiple render regions based on the viewport or the last render. It feeds the mask information to the Vray Renderer Mask and you can optimise your rendering time massively!
I've had this one under wraps for a while (I forgot I hadn't uploaded it).
Basically, just load the tool, it'll grab your viewport or you can choose last render, then start painting regions. Press "Save Mask" to put the mask on your disk/network somewhere, make sure you use a lossless format like BMP, TGA, TIF not JPEG! It'll then set the VRay Render Mask to be your new image and every time you make any adjustments just press "Update Mask"
There's some pretty useful things like if you've got MultimatteElement masks the tool can isolate the channels and contribute to the render mask for the next render. The Quick Render button will allow you to get some nice quick renders for these.
The 'Add Selected Objs' button does a quick viewport grab of the objects, this means it won't work properly for anything which shows a different mesh at render time, and I highly recommend pressing the 'Expand Mask' button to give yourself a but of buffer too.
Use with caution, this script can break several parts of your scene / custom UI accidentally if it crashes! It's fairly stable now, I'm sure there's times when the "Add Selected Obj" button won't work so let me know where it doesn't and I'll try fix it!
PS - Don't look at the code, it's pretty messy!