Android only: If you're entirely confident in your pockets, your purse or your butt being unable to accidentally dial people or launch loud apps accidentally, go ahead and grab No Lock. The Android app simply disable's Android's slider-based lock screen.
And that's the only thing it does, really, replacing the usual slide gesture with a simple button to tap. As Download Squad points out, the very nifty Tasker app can disable the lock screen, and even do so under just certain times or conditions (among many other things), but this app requires much less work.
It's a free download for Android phones, available in the Market, and you can scan the QR code at right to grab it.