I get so many coffee grounds, rabbit manure, and food scraps that my buddy and I are in the middle of setting up a composting facility in Lansing, Mi. Lots of continuous air flow worm bins and some industrial size tumbling composters. We'll be opening our service to the public this fall and will be selling our castings locally the following spring. So if you live in or near Mid-michigan be on the lookout for my posts about that, we're not gonna bother with packaging. Just come on down with a five gallon bucket and we'll load you up.
But enough about myself!
You can work some coffee grounds into your soil if it's like your soil bed outside, it will provide instant release phosphorus and potassium, along with slow release nitrogen. It's not really something you want to do for an instant fertilizer... But it's good to work into your garden bed at the end of fall when your done growing to enrich your bed for next year. I wouldn't work it into your pots tho...Unless you were doing no til gardening.
I just started a new experiment, I've taken some old soil, mixed in 10% coffee grounds, and now I'm gonna let them age for two months and see if they did anything to enrich the soil after.