There was a soundtrack ablum for Dr. Zhivago. However you can find Lara's theme on some dance CD. It's actually a viennese waltz, not a slow waltz (the melody is slow, but you are actually dancing to a more subtle underlying rhythm at viennese tempo)

For your slow waltz there's always Moon River, or "a time for love" from Romeo and Juliet. Actually a lot of recent movies have themes or major numbers that have been wonderfully re-recorded as slow waltzes by dance orchestras (the soundtrack versions are often a little outside comfortable tempo): Dances with Wolves, Cider House Rules, Shrek, Pearl Harbour, the Patriot, Moulan Rouge, Gladiator, and many more.