i gathered rainbows in my fingers on acid once, but thats about the extent of my rainbow gatherings...
the one I went to was in northern cali, the modoc national forest that was last july. next years is going to be in the greater mid-Atlantic bio-region were that is.
check the websites on rainbow stuff. http://206.168.38.1/www.welcomehome.org do a www.google.com search, there are small regional gatherings all the time