RV52.com has bought and sold several RVs with varying degrees of success. We (Sheri and I) have used this site, RVtrader, RVT, and craigslist. One of our children very successfully sold an Airstream travel trailer for substantially more than expected using eBay.

I have several articles and books that IMPACT and INFORM your selling activities:

How we bought and sold our RV with a note and never lost money
How to save 25 to 40 percent when buying an RV (the flip side helps inform you too.)
Selling and Buying an RV in California – A reader asks
RV Sales Contract Generator
RV52.com now has RVs for Sale
RV Finance : A tale of two banks
RV Buying Guide and How To Pages
Is an RV a Good Investment
RV For Sale – My elderly neighbor has an ALMOST UNUSED Class A (we sold this successfully, within 2 months of starting to try to sell it)

Far and above I've had the MOST success using the big sites (RVTrader and RVT) and limited success using craigslist.

I'll also provide a few quick hits for you that are easy things within your control to do REGARDLESS of any advertising you would do.

A good video helps a lot. We made vids of all of our RVs. If a picture is worth a thousand words, then a video must not even be measurable.
Get LOTS of good pictures. Use your phone camera and get a panoramic picture or two.
- Make the bed when you take pictures.
- Control the lighting so the outside lights don't mess up the picture (saturate is the big word here)
- If they are blurry, take it again.
- Straighten up the interior.
Measure the darned thing. Even if you can find the specs online, people will still ask.
List in multiple places. Yes it might cost you a little, but if you want to dance with the big dogs, you gotta bark.
Look out for "scams" where people try to take your money. Escrow is the #1 way to avoid this.

I thought I would list a couple easy links here (Amazon and other links disclosure) to help you get started:

Method #1 - Easy (Free, but only modestly successful) - Craigslist

If you have never been on craigslist, then start here: https://www.craigslist.org/about/sites
Otherwise you know what you are doing, right?
Beware of scams from craigslist. Beware of scams.

Method #2 - Easy (very inexpensive) - eBay

You can get started here: http://www.ebay.com

Method #3 - Expensive (expensive, but very effective) - RVT.com

I put the graphic below and you can click on it to get started on RVT.com. Far and away, I've personally had the most success paying for ads on this big site rather than from craigslist. So I guess you would say that I recommend this over other techniques.