Hitchgathering is the name of a series of international hitchhiking gatherings held in Europe and Northern America since 2008.
Mailing list
Unfortunately, the old mailinglist is down and it doesn't look like it will come back (http://lists.freeactive.net/listinfo.cgi/hitch-freeactive.net).
A new list has been created: https://lists.riseup.net/www/subscribe/hitch