The eJuice Me Up calculator is a fantastic desktop tool for designing and filing ejuice recipes. It is one of the first projects of its kind made to assist DIY ejuice recipes. There are a lot of web applications as well, but in order to work on recipes when you are offline, it is nice to have something installed on your computer.
Another benefit of the program is its ability to calculate the cost to produce many different batch sizes, and to store a library of your flavoring on hand. Check it out!