Throughout the year, we highlighted five new social media tools as part of the regular column Platform Five.

Now that December has arrived, we are bringing you the best of the best, counting down our picks for the top 20 of the year (based on a shortlist of 50 tools that you can view here).

For the first installment, we bring you Nos. 20 through 16.

Next week, we’ll unveil Nos. 15 to 11, before revealing the top 10 just before Christmas.

Here we go: The 20 most-useful new social media tools of 2011, part one:

20. SiteTrail.com. An easy (and free) way to track the performance of competitor websites.

19. Panabee.com. A domain name checker with a twist, helping you brainstorm new ideas based on URL availability.

18. FBsearch.us. Powered by the Facebook Open Graph API, FBsearch.us helps users search across posts, photos, people, pages, groups, and events without the need to login or have a Facebook account.

17. Conversocial.com. A tool to help brands manage customer service on a large scale across Twitter and Facebook.

16. Lubith.com. This is a WordPress theme generation tool that is easy-to-use and will save you time (and money).

We’ll serve up more detail about each tool as we get closer to number one!

See you next week for Nos. 15 to 11.

On the Paratus Communications blog, PR Daily Europe contributing editor Adam Vincenzini rounds up five of the most-talked-about social media platforms each week. The feature is called Platform Five. Adam has agreed to simulcast it on PR Daily. If you’d like to check out the previous editions, they’re all here for you to browse through.