Since I have posted so many different types of macro diffusers before in my blog, I thought it is a great idea to have a summary list of all the macro diffusers here for easier reference:
Macro Diffuser for pop up flash / built in flash.
Highly recommended if you already have a macro lens but no budget for a speedlite / speedlight yet.
Macro diffuser for bigger speedlite/speedlight such as the 580EX II / SB900, 430EX, SB800, SB600 etc:
Highly recommended if you already have a speedlite or speedlight and want to really try out macro before committing to a more dedicated system such as the twin flash or flash bracket.
Macro diffuser for bigger speedlite / speedlight on flash bracket, such as the 580EX II / SB900, 430EX, SB800, SB600 etc:
Highly recommended if you are serious about macro but not willing to spend money on twin flash system.
Macro diffuser for light weight speedlite or speedlight like the 270EX or similar
Highly recommended if you want a light weight macro rig that really works but won't cost you a bomb. The FMMB (front mounted macro bracket) is great if your macro lens has no IF (internal focus), as the bracket (and thus the speedlite mounted onto the bracket) will move along as you change the magnification. However, if your lens has IF (such as the Canon 100L and 100 USM), you can use a tripod collar and save yourself some DIY work. (Note: Canon tripod mount ring D is for the 100L whereas tripod mount ring B is for 100USM)
Macro diffuser for MT-24EX
Highly recommended if you already have the MP-E65. MT-24EX is MP-E65's best friend and you know it!
Macro Diffuser for Nikon's R1C1 or R1