Most of these diffusions are rarely asked for by a DP, but when they are, it's nice to know what you are talking about.  Here is the breakdown:

Rosco 3006 - Tough Spun

A slight diffuser.  Softens edge, but the beam shape is maintained.  An excellent general purpose diffuser.  

Rosco 3007 - Light Tough Spun

By the manufacturer's account, this is the most popular diffuser, but I think time has shifted that to half white (250).  This is similar to full tough spun, but less dense.

Rosco 3020 - Light Opal Tough Frost

This is a very slight diffusion that softens a beams edge.  Has a shiney side, and a smooth side.  Basically can be described as a half opal frost.

Rosco 3011 - Tough Silk

A slight diffusion with directional properties.  Spreads beam to create a wash for eliminating scallop effect created by light spaces and extreme lighting angles.

Lee 228 Brushed Silk

A thicker diffusion than the Rosco version but still has the same directional properties.  

Lee 256 - Half Hampshire Frost

Provides an extra light frost effect. 

Lee 257 - Quarter Hampshire Frost

Provides an extra light frost effect.  Just depends on how slight a frosting the DP is looking for.

Lee 258 - Eighth hampshire Frost

Provides an extra light frost effect.  Just depends on how slight a frosting the DP is looking for.