Looking for a simple way to request music on the go, try Fun Wedding, which is an app that allows you to pick from the most requested wedding tunes, not current charts. If you want classic wedding music, this is the app for you.
Shutterfly has a great resource for "Filtering Songs." The selection is not deep, but it does help you to find a quick tune for a special moment. First, pick your moment, then your genre or year and see your results.
TheKnot has a large selection of wedding playlist for themes and moments. Looking to say with a Long Island theme or you just want to see the list of romantic slow dance songs, then this resource is perfect.