I found early on in my guitar playing that the most helpful way to learn about song structure was to learn other people's songs. At the time, OLGA was the place to go for tabs and chords, but now it's a little more spread around.
911Tabs - tabs search engine // 3,500,000 tabs. Guitar, bass, drums, guitar pro and power tabs! is a pretty good clearing house for multiple tab sites (though make sure you have Ad-Block turned on as it's pop-up hell).