There are implementations which implement the standard, slight variations of it (lower case identifiers, ...) or large extended versions of it (+ MOP + CLOS everywhere + ...).
There are also derived languages like Stella, L, SubL and others which implement some kind of subset.
Then there is ISLisp, which is very similar, but slightly simplified.
Somebody probably posted a Lisp story early this morning, it got ranked highly, everybody else noticed that and jumped on the karma bandwagon by posting their own Lisp essays or just their favorite bit of 10-year-old Lisp lore :)
Remember, all it takes is one "XYZ sucks" post on the front page to get a front page full of "Why XYZ doesn't suck", "XYZ sucks super hard", "We're using XYZ at my startup", "Successful founders use ZYX, not XYZ", etc.
The problem with these "Why I love blank language" is that they don't really address real-world usages. Sure, syntax overviews and cherry picked examples that show a quicksort in 5 lines are wonderful but no one writes quicksort.
Common Lisp is a member of the Lisp familiy of languages, just like Clojure is.
[1] http://www.cliki.net/Common%20Lisp%20implementation
[2] http://en.wikipedia.org/wiki/Common_Lisp#Implementations