I'll register for the race today, but I'll reserve decisions on charity fundraising, training groups, shorter races, and several other commitments for later. Today is just a day to set the mark (beating 4:29:45) and spend the rest of the year going after it.
Registration sells out annually. In 2009, when I ran my first marathon, it sold out in late March, so it's important to get your bib quickly when the "season" opens.
In honor of registration day, I'm also going to the gym after work to put in a good hour on the belt before the Snow-mageddon begins. It's still friggin' cold here in Pure Michigan, so the YMCA is good enough for me.