Downturns are a great time to shop if you have the money, and a lot of firms took advantage in 2009. The big got huge, the medium got big, and some got more social as firms merged and gobbled up other firms. We can’t remember a year when more M&A took place.

We pulled five deals for your consideration, ranked by “interesting-ness,” not revenue:

1) Next Fifteen + M Booth

With solid tech shops Text 100, Bite, and Outcast firmly in pocket, holding company Next Fifteen expanded in to the consumer, lifestyle, and travel PR market with M Booth in the U.S., and Lexis in the U.K.

2) Publicis Groupe + Razorfish

French giant Publicis bought Razorfish from Microsoft (Nasdaq: MSFT) for a cool $530 million. While not a PR deal per se, Publicis added a lot of size to its Vivaki suite (see VivaKi’s Superfriends of Social Media Get REAL)

3) CRT/tanaka + Livingston Communications

CRT Tanaka bought Geoff Livingston‘s firm in the Spring, along with his very popular Buzz Bin blog (now with multiple authors.) Look for the social big foot’s new firm sometime in 2010.

4) WPP Group + TNS

After a lot of chatter and speculation, global conglomerate WPP Group (Nasdaq: WPPGY) acquired Taylor Nelson Sofres (TNS), known for their Cymfony analytics tool. WPP has countless marketing brands in their stable, including huge PR shops such as Burson-Marsteller, Hill & Knowlton, and Ogilvy PR.

5) Middleberg + Dowd

The growth of Don Middleberg‘s firm is deja vu all over again. Ten years ago he sold the $18 million Middleberg & Associates to Euro RSCG. Now his Middleberg Communications reaches mid-size with the acquisition of Jim Dowd‘s firm. It’s Middleberg’s third purchase in as many years.