Nath:
Below are some sources to get you started on the first part of your question, which I guess is the main part, about punk rock's relation to political movements and activism such as Black Bloc or the wider anti-globalization movement.
As far as links between Radical Reference and the social groups you mention, I'm not sure how to answer, for two reasons: First, Radical Reference is a loose and widely scattered group, and I am not qualified to speak for it's members. Radical Reference came together about a year ago during the last US elections [Note from a founding volunteer: We formed to support and join the protests against the Republican National Convention in New York City.], and from the meeting I attended seems to be a diverse group in terms of age and cultural/subcultural backgrounds. Second, the groups you mention - Travellers and Crusties - are really UK phenomena that don't really have analogs here in the US. My understanding of those groups is that they come out of a longer tradition dating back to the festivals of the late 60s and 70s, sort of a hippy movement but in the better sense of that term, but who have held on to an alternative culture throughout the shifts in popular cultural styles and have incorporated the punk and rave scenes. But as I said, that's really a UK thing that we're not that familiar with here. If you could clarify your question a bit on that aspect of the topic I'd be glad to help some more.
So, for now, here's a start. Look it over and let me know if this is what you were looking for, or if it's not quite right tell me what's missing and I'll take another crack at it.
a website, with other links to start from
blackrose article on Black Bloc
anarcho-punk article in Wikipedia, cites Crass, includes links to other anarcho-related entries
infoshop.org's "black blocs for dummies"
paper from the archive of the "Society for Social and Political Philosophy":
Black Bloc, Pink Bloc: Reflections on the Tactics of the
Anti-Globalization Movement
author: Marcos Bisticas-Cocoves
books that might be good:
articles from journals:
the endnotes from any of these articles will be a good place to look for further resources