Alphabetising Category List

Hey, just after a little help.
I don’t like the order that the categories are listed in on the main page of my website. As far as I can tell, the only way to change the order is to manually change them all through the Dashboard, which would require a lot of work (re-categorising 100 or so posts).

So all I’d like to do is figure out how to change the order of the list. Alphabetising would be fine, but preferably I’d rather be able to choose the order myself.

I’ve searched around and can’t find anything, but if someone could point me in the right direction, I’d greatly appreciate it.