With pyRenamer you can change the name of several files at the same time easily.

→ You can use patterns to rename files.
→ You can use search & replace to rename files.
→ You can use common substitutions.
→ You can manually rename selected files.
→ You can rename images using their metadata.
→ You can rename music using its metadata.

It is written using PyGTK for the GNOME desktop, altought it will work in any PyGTK enabled environment (KDE, XFCE, even Windows), and it's licensed under the GPL.