ReNamer is a very powerful and flexible file renaming tool, which offers all the standard renaming procedures, including prefixes, suffixes, replacements, etc

Ant Renamer is a free program that makes easier the renaming of lots of files and folders at once.

Rename Master is a bulk renaming software.

Bulk Rename Utility takes the pain out of renaming and managing files and folders, assuming you can get past the frightening user interface.

Flexible Renamer is a free tool for renaming files and folders, either singly or in large batches, including subfolders.