set.seed(1)
mdat <- data.frame(x = rnorm(100), y = rnorm(100), z = rnorm(100),
                   cluster = factor(sample(5, 100, TRUE)))

library(ggplot2)
library(gtools)
library(plyr)

cols <- c("x", "y", "z")
allS <- adply(combinations(3, 2, cols), 1, function(r)
    data.frame(cluster = mdat$cluster,
          var.x = r[1],
          x = mdat[[r[1]]],
          var.y = r[2],
          y = mdat[[r[2]]]))

sc <- ggplot(allS, aes(x = x, y = y, color = cluster)) + geom_point() +
      facet_grid(var.x ~ var.y)

library(lattice)
sc3d <- cloud(z ~ x + y, data = mdat, groups = cluster)

library(gridExtra); library(lattice); library(ggplot2)
grid.arrange(xyplot(1~1), qplot(1,1))