XMolView is very intuitive with a minimal user interface.
xmolvis is the next generation of xmolview. It very easy to use with direct keyboard commands.
Open an structure file and try the folowing 1 key commands:
1. v (volume)
2. s (atomic symbols)
3. f (fragments)
4. t (tools)
5. k (control panel)
6. b (bonds)
Try the folowing 2 keys commands:
1. Ctrl + f (compute fragments)
Older documentation and instructions:
and Save Files