If you are currently marketing on Facebook with the Facebook Ads, there are two sites that you ought to bookmark today to help you get the latest trends happening (= more exposure and targeted for your Facebook Ads).
Not many sites have recommended the first site so I would suggest that you make good use of this resource (and make more money out of it) before the whole community of Facebook Marketers know about this and jack up the Cost-Per-Click (CPC).
The First Highly Recommended Site: Booshaka.com
I would highly recommend this site because of the ability for you to do searches right off the site. For example, Jonathan Volk of the Facebook Ads Guide shared that one of his long term campaigns that have proven to be profitable is “scholarship offers”
So this is a search done over at the site and what is being generated:

There’s more results being shared and you do have to search on your own to appreciate. I would say that the results are very relevant and real-life. And the results shown are mixture of Pages and Posts so you have a rough guide to understand if your Facebook Ads have any tough competitions or appeal.
No Ads In Mind. Then Check Out The Sections…
If you do not have any specified ads to create, then you may wish to check out the Sections
I checked on the Games Section and this is one of the results shown:

So if you have any Game Offers (on an iPhone or Android) that’s similar to the Game above, you will know that your Ads are in the Trend. If you are into Mobile Marketing, this will give you a good exposure as well!
When Things Are Too Good To Be True…
Though Booshaka.com may sound too good to be true, there’s some feedbacks given on the search results as well. These feedbacks are saying that it may not be 100% accurate – some commented that they have joined a popular Facebook Page that’s not listed in the search results.
My Suggestion to you is not to take the results too one-sided, nothing is perfect. If you are indeed getting results that’s not listed on that site, you may wish to give your feedbacks to the site owner. They will appreciate your opinions on making the site better!
Also if you do have a Facebook Page that’s so popular but not listed and there’s many people talking about it, at least you know that you have a “Gem” on hand! I would rather you keep it a secret and learn to market your products on it.
The Second Recommended Site: ItsTrending.com
This site has existed much longer than Booshaka.com so you may have taken note of this site before.
Not much functions on that site but its layout is similar to those of Digg, Stumbleupon. The results shown are of those “most shared”, meaning Trends that many people are sharing among their friends.
But a good thing function that you would like to take out of the site is the ability to discuss on the results directly (not something new but still useful) – you (creating your own Facebook Product Profile) can make good use of this to “get more friends” (more chance to expose your services)
