It began last Saturday and it's expected to reach Brussels on September 27 after many journeys varying from 17 to more than 50 kilometers, mostly through France.
People who wish to join for whatever length is asked to write to firstname.lastname@example.org, including name, mail address, telephone and journeys planned to take part in, or calling to telephone +34-679213259. Marchers are expected to bring their luggage, shoes, basic aid kit and sleeping utilities (sleeping bag, tent). A van accompanies the march to take care of luggages and people who need to rest.
The slogan is "March to Brussels. Against labor reform, for social rights" and one for the callers is anarcho-syndicalist union CGT, a splinter of the historical CNT (they mention other organizations but I have not been able to find out yet).
More photos and info (in Spanish) at CGT (includes detailed schedule and other info) and Rojo y Negro (photos).
From the second site:
We march against the spoliation of working classes and the destruction and privatization of the public sector in all Europe.
We march against Labor Reform and social cuts in the State of Spain.
We march against the Spanish government and the rest of European governments, who reduce salaries to public employees, freeze salaries, freeze pensions, increase VAT equally for the rich and the poor.
AND ABOVE EVERYTHING ELSE, we march because taxes are not being raised for the rich, fiscal paradises are not being destroyed, submerged economy is not being persecuted, tax fraud is not being attacked, no responsibilities are demanded to those who have caused the crisis, no embargoes nor prison are being applied against bankers, speculators and billionaires who are taking the public money.