MODO | V-Ray 2-Sided Material
V-Ray has a 2-Sided material with a translucency option that works well for leaves. You have to set it up in the schematic though - so it's worthwhile watching a tutorial. The first 9 minutes go through a lot of render comparisons to show the effects of 2-Sided materials and translucency. Fast Forward to 8:53 for the schematic set up.
