From my big Webster's:
Progression -
1) a moving forward or onward; progress
2) a sequence or succession, as of acts, happenings, etc.
In a sense of definition 2, the terms "progression" and "evolution" can be considered synonyms - They are both change through time. And the theory of evolution has itself indeed evolved.
In the sense of definition 1, there also has been progress in the theory of evolution, in that there has been an increase in the understanding of evolutionary processes.
Of course, my literalism here is not in line with NosyNed's intent of the topic title question.
I think that a progression can be progressive, regressive, or neutral (just like a mutation).
Much good stuff has been said upthread, but I thought I'd throw in this bit. Perhaps I've fallen a bit under the influence of Brad.
Moose
Professor, geology, Whatsamatta U
Evolution - Changes in the environment, caused by the interactions of the components of the environment.
"Do not meddle in the affairs of cats, for they are subtle and will piss on your computer." - Bruce Graham
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