Guest list and invites is the next big one, as until you know how many people you have coming it will be difficult to organise food, drink etc.
Also never to early to pick bridesmaid, best men etc.
Always good to book the following people early as well: Photographers, caterers (unless venue is catering) and bands / DJs. And of course looking at wedding dresses, which is the fun bit!
Hope that helps a bit? :) x