There's also the version of "The Purple Dancer" on the 2/71 bootleg of the Swing Auditorium show in San Bernardino, the first show the band did after Jeremy Spencer left. Christine McVie sings Jeremy's vocal parts on that version. This recording has been available for download in the past, don't know whether it still is:
http://ledge.fleetwoodmac.net/showthread.php?t=23578
And FWIW, my favorite version of "World In Harmony" is the live one from the Tea Party Club in Boston in 2/70 that somehow didn't make it onto the remastered
Live In Boston discs from Snapper. I posted about that a few months ago, and I'm sure there are still plenty of those older Tea Party live discs available that have that version on them:
http://ledge.fleetwoodmac.net/showthread.php?t=31625