I keep seeing questions on the interwebs about queuing up songs on the fly with iTunes on the iPhone/iPod touch. Here is my idea Apple:
Add a function (could be you and hold to bring up the option or adding a number beside the individual song in song list) that allows you to select a "play next" option.
This would allow you to add songs in the order that you want to listen when you are in the middle of a song and think "Fuck, I want to listen to (blah, blah) after this, but I don't want to accidentally select it yet".
Make this happen, free idea!