SQL Developer 3.1 has been released with a number of new features for DBAs. I have been using the Early Adopter/EA versions and I find the Data Pump wizards useful for quick cheap exports and imports. Tim Hall plays and displays the Data Pump wizards here:
ORACLE-BASE - SQL Developer 3.1 Data Pump Wizards (expdp, impdp)
You can see all the new features here.
Most useful I think is the RMAN and Data Pump integration. There is an improved database diff and a few other things. Definitely worth downloading and updating your current version of SQL Developer