How can I scrobble my music to Last.fm? Is there any way to scrobble the songs I listen to on my Android phone to Last.fm?
The easiest way is to install the official Last.FM app, this will scrobble tracks played by the default Android music player, as well as from many 3rd party audio players, like WinAmp.

It doesn't work with some manufacturer customized music player apps (for instance, Samsung have modified the music player app on the Galaxy S's and scrobbling doesn't work from there). I use WinAmp to play my music on my phone, and that happily scrobbles via the Last.FM app.