Built-in or FOSS GUI application for generating a file hash I would like to know if there's a built-in GUI application in Mac OS X that can generate file hashes (Disk Utility?). If there isn't such a built-in application, does a FOSS alternative exist?  I can accept any application that can generate a file hash as CRC, MD5, or better in the SHA realm. 

Additionally, showing how this is done in the application would be a bonus.
If you want to find a method of converting general CLI scripts to the GUI, take a look at Platypus. Using this application, you can create GUI wrappers around CLI utilities. It's fairly straightforward to make a shasum or md5 wrapper that can allow drag and drop.

However, there are existing applications available to show file hashes (see Allan's answer).