If you've been procrastinating, haven't done your taxes and are freaking out now, don't worry--there's an app for that. GottaBeMobile has found a 99-cent iOS app called Taxsoftware.com 4868 that makes filing an extension using Federal Form 4868 super easy. The extension will extend your due date to October 17, 2011, but there are some stipulations if you owe taxes.
If believe you're going to owe--which means you'll have to at least start your taxes to figure out or base it on your 2009 taxes-- you have to pay the IRS along with filing your extension. If you can't afford to pay everything owe today, don't worry. As long as you properly estimate your tax owed, Form 4868 states that you must pay at least $1 (but ideally more) with a debit or credit card when you file for an extension online. Just keep in mind that you'll still be charged interest between now and October 17, 2011.
If filing an extension through your iPhone, iPod Touch, or iPad seems too radical, GottaBeMobile has a list of other ways to file for an extension both online and off. Plus, the IRS's website, irs.gov, is-- somewhat surprisingly-- very helpful and well organized, with PDF versions of tax forms and useful answers to frequent tax questions.