eti is a california-based organization (i think it's only calif., anyhow) that stands for equestrian trails, inc. we are organized into corrals (i'm in the shadow hills "rough riders" - corral 20). the org. has been around for a long time. i belonged to another corral some 25 years ago, too. different corrals emphasize different things. some are more english related, some more western. ours does a lot of playdays, trail trials (i have yet to compete in a trail trial), horse shows, gymkahnas, group camping trips, trail rides, and so forth. our corral also does trail maintenance once a month. each year there is a big state-wide eti convention at the los angeles equestrian center. TRAP is a program sponsored by eti. you log your trail hours, and they keep track, too, and send the info to govt. agencies to raise awareness of horse-related use of trails and so forth. you get patches and stuff for participating. i believe the aqha also has a trail use program. i see it advertised in magazines. the los angeles chapter of the sierra club is also very involved in trail building. it's more hiking oriented, but they do a lot of business w/equestrian groups for trail preservation, and work together to keep mountain bikes off of single track trails. hate bikes on hiking/riding trails. i met my dh trail building w/the sierra club. so did my mom, come to think of it! there are many bike orgs (such as corba in calif) that purport to want to work "with" hikers and equestrians to build trails. they just want to co-opt as many trails as they can.
jo