SuperSFV is a Simple File Verification program for Mac OS X. It has an intuitive drag-and-drop interface, somewhat based on Transmission's and is released under the GNU GPL. Although I admit the source may be a bit sloppy, it is included in the download.

SuperSFV tries to add on to the SFV format by allowing the MD5 and SHA-1 algorithms to be used for verification as well as the standard CRC32. The format is still shallow, however.