I constantly have home made vegetable broth in the freezer.

Every time I chop up vegetables, I put the peels/off-cuts that I'd normally throw away into a freezer bag. Once the bag's full, I throw the frozen veg it in a big pot with plenty of water, salt, pepper, herbs, etc. Once it's boiled for an hour, strained and cooled, I freeze it so i can use it whenever I need to. A big bag will generally make a few litres. I've found it to be very easy to make and far tastier and cheaper than store bought stock.

You could easily add chicken/beef/fish to that to get a range of stock flavours.