I find Freak Out! to be better than In it for the Money. It is along the same line, but with better and more entretaining songs.
Frank's 2 most accesible records are Hot Rats, the album that initiated jazz rock (I dont mean it is the first how could I know) containing the masterpiece Peaches En Regalia, the Zappa classic Willie the Pimp (features Beefheart) and one of the dopest jazz rock jams The Gumbo Variations.
The other record is Apostrophe, even more accesible than Hot Rats, it has the structure of a storybook, Frank is telling a hilarious story about an eskimo in his first 4 or 5 tracks, set to sensational music. The rest are other stories, about jivin gypsies and fido the talking dog, plus the phenomenal rocker with the album's title.
Other personal recomendations are:
Freak Out!
Zoot Allures
Sleep Dirt (this is an odd Zappa album, it has pretty emotional tunes, not very characteristic of him)
Overnite Sensation
Sheik Yerbouti
Peaches En Regalia
http://www.youtube.com/watch?v=v-cEkk-n8OA(which is also my favourite videoclip)