We got lucky.
Thousand Trails was recruiting at the Big Tent in Quartzsite and got us into a neat summer job.
We also signed up for the news letter at
http://workamper.com. That site puts out news of job openings several times a week. The site also gives you the capability to build a resume on-line that prospective employers can see.
Another site to visit is
http://www.recreation.gov. This one can get you into national parks all over the country.
These are just a couple of locations to explore. Once you start looking, you will find that there is an abundance of positions available as long as you are ready, willing and able.