Watched this video in 1991.  
These 2 guys come out of a building and they witness a girl being
slapped by another guy.  One of the 2 guys comes to her rescue and
later falls in love with her.  Little does he know that she is
involved in some cult/witchcraft and his friend is the leader of this
cult.  At the end of the movie they're doing some sacrifice ritual on
the beach where the girl is dancing around him as he's laying on the
beach and his friend reaches in his chest and takes his heart out.

Hello.

I believe that your movie was "Spellbinder" (1988).

From the Internet Movie Database:

"When Jeff and his friend rescue a young beautiful woman (Kelly
Preston) from an apparently abusive boyfriend, the trouble starts.
Jeff unknowing becomes involved with Miranda (Kelly) and the web of
intrigue that follows her. Miranda is on the run from the witches
coven (to which she belongs). Miranda tells Jeff of her situation, but
not the entire truth. Jeff willingly helps Miranda out of her
troubles, but creates his own."
http://us.imdb.com/title/tt0096152/plotsummary

More details at Amazon:
http://www.amazon.com/exec/obidos/tg/detail/-/6301300521/

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search strategy: 
google groups: rec.arts.horror.movies "satanic cult"

If you have any questions, please request clarification. Thanks.

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Request for Answer Clarification by laurac-ga on 18 Mar 2005 21:52 PST

You have given me the right answer!!!!  Thank you so much!!

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Clarification of Answer by juggler-ga on 18 Mar 2005 22:00 PST

You're welcome. Thank you for the tip.
-juggler

Thank you!!  You have given me the correct answer.