Many people don't realize that you do have a swing. While you may not feel your vote matters in some of the larger elections, presidential being the most popular, registering to vote also gives you the ability to sign petitions.
Just today I stopped on the side of the rode to sign a petition to recall the governor of Michigan who is hitting our public education system with some serious cuts.
If I would not have registered to vote (I do it when I renew my vehicle tags every year) I would have not been able to sign that petition. Many petitions comes down to a few hundred - thousand signatures.
Even if you have no desire to keep up with politicians or to vote for them, you should still consider registering. You never know when an issue may come up that effects you directly!