Shopping for an RV online
Here are online places I've found that tend to have something close to what I am looking for in an RV:
Craigslist Has all the advantages and disadvantages of a free ad site. Mixed personal, dealer, and scam ads. Doesn't have an index, each "city" covers only a small area. Many people don't do a good job describing their vehicle, and some obviously don't know what they have. Prices range all over. Tends to mostly have cheaper older vehicles.
Craiglook A search site for Craigslist ads. Allows you to search over a wider area, but depends on people puting the keyword you search for in the ad title. The search result display has more useful information than using Craigslist directly. Update Due to a disagreement with Craigslist, this site has mutated to Claz. It now no longer has craigslist ads directly, and combines several other search sites, at least one of which had craigslist ads. Unfortunately the triple indirect almost always fails and the site is not very usable anymore.
RV Trader Online Paid ads, mostly from dealers. The search is much more useful, since there is a database with things categorized. Lacks most of the bargains and scams found on Craigslist. Having a recent updated date does not mean the RV hasn't been sitting on the lot for months or years.
Ebay Motors It's Ebay with both auctions and fixed price items. I'm not going to buy an RV without looking at it and test driving.
update Oodle Another combined search site, but this one seems to be mostly working (except rvtraderonline listings).
For a vague idea of what an RV might be worth, based on the model and year, there is NADA guides. While many say the NADA prices are high on recent vehicles, I think they tend to be low on older ones in good shape. (Perhaps they are averaging in the ones in poor shape that I wouldn't consider buying.) The free online version does not include the wholesale prices that dealers use for tradeins and banks use for loans.