This depends where you live. I can only speak from my point of view in America.
For America, some large influences were obviously the wars in Iraq and Afghanistan, 9/11, the Bush presidency, climate change, completion of the Human Genome Project, Cell phones, the dominance of the internet, the stock market collapse, and the election of Barack Obama (it's funny to me that that name still gets caught by the spell checker on Firefox).
I think consumerism has become more prevalent in the 2000's. The 90's seemed to have a backlash against the consumerism of the 80's, with generation X being that popular 18-34 year old age range
during the 90's. Music was often either about the struggles of being poor (hip-hop) or about how shallow and unfulfilling consumerism and mainstream society is (rock music). I think the internet getting big, and it's subsequent shopping sites and advertisement opportunities, created a new consumerist bubble.
The 2000's was definitely the first digital decade. Cell phones both dominate peoples social lives and television commercials. I think the emergence of cell phones (eg smart phones) and similar electronic devices has also added to the re-emergence of strong consumerism - everyone wants to latest iPod, smart phone, Kindle, notebook computer etc.
People now spend a great deal of time texting, updating their social network page, and blogging/tweeting about whatever comes to mind. This has led us away from any semblance of an information age and shifted the paradigm into an
opinion age. Everyone now has instant access to the opinions of millions of people on any range of issues. This has brought both a polarizing of ideologies and yet, at the same time, a
leveling (in the words of Soren Kierkegaard).
I think the 2000's was also the decade when America really felt it's self-proclaimed spot as the world leader being threatened. Not only was America attacked within it's own borders (9/11) but other powers (China, India) became a lot more powerful. I think this has added to the partisanship in America, because there are a lot of people who refuse to believe that America isn't and always will be "number one."
Speaking from my own personal experiences, I've seen a trend in hip-hop music becoming extremely mainstream. I remember the 90's as an era of more underground kinds of sounds with Wu-Tang Clan and their various affiliates, Canibus, and the emergence of JMT, Atmosphere, Aesop Rock and so forth. The 2000's were when pop music seemed to shift from boy bands, Britney Spears etc to mainstream hip-hop and R&B music.
The hipster look seems to have become popular in the 2000's. When I was in middle school and high school during the mid to late 90's, most people either looked grunge/punk or
90's style hip-hop (oversized clothes, t-shirt, sagging pants etc). A lot of the younger people I work with, and the people my younger sister hang out with, have the
stereotypical hipster look.
The 2000's have been marked by a lot of re-tooling of old stuff. A lot of the movies that came out in the last decade have been sequels, prequels, remakes, and comic book films. A lot movies now days seem to be plagued with computer generated special affects (live action movies are almost cartoons now) and gimmicks like 3D.
I think, to sum it up, the main theme of the last decade is technology. I don't think anything has shifted the paradigm more than the technological advances during the 2000's.
edit: I forgot to mention (or maybe I suppressed it) the 2000's was an era fraught with "reality" TV. It pains me to say it, but it was big enough to be worth mentioning.
