Renaming files in Windows Explorer is somewhat slow - select, F2, type a new name, select the next file, and repeat. I thought it would be cool to instead use a spreadsheet interface - where pressing Enter drops you down to the next line.
So, I wrote RenameCells, a Python program for quick renaming. I also added features for batch renaming like Rename by Pattern, Replace, and Regular Expressions. You can see all of the changes in a grid before you press Rename. The grid interface also lets you copy and paste from Excel or another program. See the tutorial for information about all of this.
Update! In 2012, I moved this onto Github!
Tutorial explaining use.
Download for Windows (just unzip it and run RenameCells.exe)
Python source, cross-platform, requires wxPython.
Update -- this is now on GitHub, and I use it frequently: Downpoured at Github.