Twitter. It's one of those things that people don't 'get' until they try it. You update your status in 140 characters at multiple points during the day with events as mundane as feeding your cat.
However, twitter has become more than this. Unfortunately, I've not been using it long enough to see it's evolution, but there are a could of 'extra' functions that end-users have created which help organize this mountain of information. My handle on twitter is 'andylockran'; if someone wants to address a message in my general direction, but wants others to join in the conversation, they'll prefix the message with an @. If they want it to be sent to me in private, it'll be prefixed with a 'd ' - and if they're talking about a general topic, that others could also be talking about, it's prefixed with a #.
Whilst I was at university, one of the assignments set was to examine the level of information that people were happy to publish about themselves on Internet forums. This was in 2004, with the heyday of the 'Internet forum' being the mid-late 90s. It was an interesting task though, as it was pre-'general release' facebook and I didn't go to a University esteemed enough to be included on facebook until just before the 'general release.'
One of the things we noted was that people were able to put so much personal information of forums, and much of it was irrelevant to the particular topic being discussed - but by putting it out there people were dealing with their issues. Rather than holding information inside and trying to repress it; publishing this information was a form of therapy. With twitter, it's easy for anyone to publish information and with something as simple as a # sign, you can immediately converse with a group of people who have a shared interest. I don't use them alot, but being able to access a group of people attending the current CES show, I just type #ces or #ces09. There are even sites that scan the blogosphere looking for these tags - so hopefully if someones demonstrating this in Vegas, they may accidentally stumble across this blog!
Something I've blogged about before, is the idea of the 'Long Tail' - Chris Anderson. This is where people who would have been seen as uneconomically viable in production of a capitalist nature are now able to contribute, no matter how small their contribution, in an economically viable way. Their contributions may be small, but their combinations may unlock something much bigger. With the information and infrastructure afforded to twitter users, it is no longer 'taboo' to try and get in touch with someone else suffering from a similar ailment. Tag your posts with the ailment, search for people by location, and you've immediately found yourself a local community and therapy group.
The ability to do things like this is unprecedented, and we're moving at such a fast pace that there is rarely a week goes by when I realize I could have used the Internet to do something more powerful that I would have ever thought. It also helps that the tools for manipulating this information are getting easier. python-twitter is a very easy api to learn. When you put that with ipython; a python shell that provides tab completion, and a useful help() feature, I could put most of my peers in front of a computer and get them to download and create graphs of tags .etc from the twitterverse. with little tuition.
The other thing regarding twitter, is that you get a three dimensional view of issues, both quantitatively and qualitatively. If you want to grab a load of stats for illnesses, there's so much information out there passing through the RSS feed every minute, that doing so for a week would give you a massive sample of information. Conversely, you can pick one person from that feed and analyze their twitters longitudinally. Because all the information is in the public domain, this is entirely legal.
So if you're a psychology student now, sitting down to write an essay on psychology and the internet - may I suggest you take a look at twitter, as it's almost the perfect platform for this sort of work. I wish I had.