Curious to what applications your using for SPF

Hello,

I have been searching around for applications that implement SPF for 
sendmail.  The download page on spf.pobox.com, milter.org, google 
searches, libspf2, all present quite afew options or other places to look.
I have installed libspf2 and spfmilter thus far.

An application in C would be best for me at this time.

Your comments, suggestions are welcome.

Thank you,

Michael...