Renamerator
Maybe I'm just a little overly compulsive but sometimes I want to rename a bunch of files. I could go through, one at a time, and rename them all by hand but if there are many files this takes a long time. So I built this file-renaming utility and I added some "features".
In addition to simple text replacement you can use regular expressions. There are also a handful of macros you can insert into file names (file size, file dates, random numbers, ordinal numbers, every possible JPEG EXIF value that exists and a slew of MP3 ID3 tags). There are a few sample replacement commands (Help > Examples) to give you an idea of what's possible. It will also recurse subdirectories (but will not rename the directories themselves).
Requires the Microsoft .NET Framework(v2.0)(v4.0).
v1.4.2 Fixed registry problem under Win 7 (and probably also Vista).
v3.0 [July 17, 2012] Upgraded to the 4.0 .NET framework. Fixed the ability to register Renamerator in the Windows Explorer directory context menu (i.e., "right-click > Renamerator"). Selection state is now preserved through rename operations. Duplicate rename operations are handled slightly differently (end user is alerted before the duplicate files are renamed rather than afterwards).
v3.1 [Dec 28, 2014] Added MOBI meta data properties.