I didn't intend to kill this one stone dead, but there are useful Classifieds on the internet as well.
Here's an idea which works:
Expats (of any nationality) are a good market. They're often on generous salaries, allowances and holiday entitlements. There are dozens of expat forums in any country you can think of. Use Google to find them. Some are dire, some are good.
Switzerland is a good example, several forums, and punters hungry to escape the cities. Some forums have classified attached to them.
If your property is within easy reach of Geneva (good motorways into France/Italy, TGV runs into Geneva and Lausanne, EasyJet have an expanding base), for instance, try this list -
Classified Switzerland. It's free, you're allowed images, you're allowed to mention your website and I'm working on the owner (Louisa - beyond helpful) to allow proper outbound links and Holidays as a separate category (rather than Accommodation). You get a hit counter, and remember to renew each month. Response is good. Ours is
here.
Good luck. She's got another site, more commercial - details to follow.
MG