From my experience, Superstudio used to be known only from their influence on architects like Koolhaas and Hollein. (Compare Koolhaas' Exodus with the more architectural works by Superstudio for example). Lately however, there has been a lot of interest in revaluing these and other "para-architectural" groups of the sixties and seventies, like Archizoom, Haus-Rucker, early Coop Himmelb(l)au etc. For me, these projects still have an enormous power and provocative edge (especially Superstudio), but they had much more influence in their own time. Now they are rather seen as an important part of the history of the discipline, although I sometimes find they are better in describing our present condition than our contemporary "digital architecture" theorists.

To my surprise, I recently stumbled over the contemporary works of Andrea Branzi (of Archizoom), to find that someone is still continuing to design in a similar manner. See the latest Domus for more info.

If you're into that, you should probably look toward contemporary art more than architecture firms. People like Gianni Petena or superstudio had more influence in art galeries than in architecture practice and on society in general. Artists like Thomas Hirschorn (not sure of the spelling) or Van liesout are the logical followers of the 60's radical movements. They design spaces that are polemical and don't have to deal with the regulations and security issues that architects have to confront to. There are of course "firms" like stalker in Italy and such, but that when you start asking yourself the question if its really an architecture firm...

The pseudonym "French" reminded me of the book "Superarchitecture - le futur de l'architecture" from Edititions de la Villette. I'm still struggling with the language barrier, but it seems like a good read!

i've worked with stalker in italy, there big influences are the SITUATIONIST MOVEMENT and a dude named CONSTANT or something. They definatly have the utopic ideal but not so much in built work and form making but in addressing social shortages particularly among nomadic and displaced ethnic groups such as the gypsies and serbians in Rome and the arabs in sicily and southern Italy. But they are a really cool and fun group.

a-f
It is indeed a very good book, trying to find a coherence in a very complex history of radical architects, starting from the early smithon, flying through metabolists and of course, Constant's work, Archigram, superstudio and such. Not too difficult to read if you know a little french I think, since it doesn't try to elaborate a complex theory but more to find the continuity in an apparently rather discontinuous history.
But the book that was published last year on superstudio is very good too, eventhough it focuses on a single body of work. and this one is in English. The catalog from the Archigram retrospective from 1999 I think is also worth checking, although it only contains original texts and projects from the architects.