Usually to get news on one of these specialties you need to figure out what phrases they use to describe themselves. I've searched for ages for something until I stumbled on the exact words my target would use to describe its services, and then I found a ton.
What I just did when I read this was to do a Google search n the phrase "product placement" +celebrity. I found several things right away - like this interesting article at
http://tinyurl.com/ctree about a very high ticket version of this kind of promotion. There's also this:
http://tinyurl.com/7cfeg which describes one of that company's promotions, and this:
http://tinyurl.com/7rytx which is a news story about how the selfsame company is being sued by the producers of "The Apprentice". There's a lot more results - maybe even something we could use

- but those popped out right away. Neat!
Edited to add more:
http://tinyurl.com/c6j4n is another company that sounds like it's for real; they list ongoing productions and what sort of placements are available. This is more geared toward getting products into movies and television shows.
This
http://tinyurl.com/ds9ht on the other hand is a whole bunch of good information on placements at, for example, the Academy Awards, MTV, and VH1 events. There are some comments at the end - the one I like says that it's probably more useful to give your product to 100 regular people

. This whole business sounds like it's full of smooth talkers and shysters and a great way to lose your, um, shirt. But on those occasions when it works it must be amazing.