Avatar Crop is a Drupal utility module based on jQuery that lets you crop your profile images when you upload them.
Just download and activate/enable module. Go to Edit account page and upload your profile picture using crop functionality. Make sure user picture settings have been done already in User settings, like picture support is enabled as well as you have set "Picture maximum dimensions" value. enjoy ;)
5.x beta version is available now. To use 5.x version Jquery update module version 5.x.2.x is required.