It's never too early!
I'm not getting married til next year either, but I've already started my plans. The sooner you start, the better chances you have at booking things for your wedding and whatnot. Firstly - congratulations!!
The first thing I started thinking about was dates that I'd want to get married. Dates mean a bunch to me, because I know we'll be celebrating our anniversary every year for the rest of our lives, so I wanted it to mean something to us. After you've picked the date, start thinking about venues for both the ceremony and the reception - or you can have them in the same place! After you see the venue, you can pick colors, your bridal party (bridesmaids, maid of honor, best man, groomsmen, maybe flower girls and ring bearer), maybe you want a themed wedding? Pick a theme if that suits you.
You can design a save the date card to send out towards the end of the year, maybe start looking at dress ideas. Think about how you want the ceremony and reception - in a church? Religious? Civil ceremony? Anything cool/out of the ordinary, like a colored wedding dress?
A GREAT place to start out is theknot.com... they've got lists, ideas, pictures of all kinds of weddings.
If you're looking for something more upbeat and risque - look at offbeatbride.com. They've got some crazy awesome ideas!