creating gradients, for whatever purpose, is something that takes 10 seconds in photoshop for me and there is no real reason to save them? I like to create two layers and fill them with the colours of my choice. I use a gradient mask to blend them together. this gives me a good deal of control over the gradient and I can modify colour intensity, shade, degree angle and % proportions of the gradient really easily.
If there is a gradient that I truly love then I will save it for future use. Most of the time I start off from scratch how ever www.styleselect.com has some layerstyles you could use in your designs if you are having trouble.
I got like 5 gradients. I don't really see any point in saving the new ones. It takes like 10 secs to make a good new gradient and I barely use any previous gradients again. B/W is the most used for me.